Recent dictionary treatment of 'furor' and 'furore'
Merriam-Webster's Eleventh Collegiate Dictionary (2003) has the following entries for furor and furore:
furor n {MF & L; MF, fr. L, fr. furere to rage} (15c) 1 : an angry or maniacal fit: RAGE 2 : FURY [definition] 4 ["a state of inspired exaltation : FRENZY"] 3 : a fashionable craze : VOGUE 4 a : furious or hectic activity b : an outburst of public excitement or indignation : UPROAR
furore n {It, fr. L furor} (1790) 1 : FUROR 3 {"a fashionable craze : VOGUE"} 2 : FUROR 4b {"an outburst of public excitement or indignation : UPROAR"}
Several things are noteworthy about these entries:
- MW traces furor's lineage to Latin via middle French and furore's to Latin via Italian.
- It identifies furor as having entered English in the fourteenth century and furore as having Entered English by 1790.
- Both definitions of furore that MW lists are particular definitions of furor—that is, furor has five distinct meanings in English, and two of those are the only MW-recognized meanings of furore in English.
- None of the definitions listed in the two entries is obsolete, which suggests that the premise in the original question that the meaning "enthusiastic popular admiration" has dropped out of use in English is not valid.
The American Heritage Dictionary of the English Language, fifth edition (2010) generally agrees MW, except that it characterizes furore as a chiefly British variant spelling of furor in two senses of the latter word:
furor n. 1. A general commotion; public disorder or uproar. 2. Violent anger or frenzy. 3. A fashion adopted enthusiastically by the public; a fad. 4. A state of intense excitement or ecstasy.
furore n. Chiefly British Variant of furor (senses 1 ["A general commotion; public disorder or uproar"], 3 ["A fashion adopted enthusiastically by the public; a fad"]).
This agrees in most ways with Merriam-Webster's treatment of the two terms, although it places the "uproar" sense of furor first instead of last chronologically, clouding the question of what the original meaning of furore in English was (AHDEL cites "senses 1, 3" of furor as the meanings of furore, without specifying which sense came first in English).
Neither MW's nor AHDEL's treatment of furor and furore addresses an important etymological question: Dids furore introduce its two current meanings ("vogue" and "uproar") into English, only to have furor appropriate them into an expanded set of meanings, or did furor contain both of those meanings all along? Let's look at some older dictionary definitions.
Older dictionary treatments of 'furor' and 'furore'
The earliest general dictionary entry I can find for either word is from Edward Phillips & John Kersey, The New World of Words: Or, Universal English Dictionary, sixth edition (1706), which offers entries for furor and for the medical term furor uterinus:
Furor, (Lat.) Fury, Madness, Rage.
Furor Uterinus, (i. e. Womb-fury) a strange Distemper, which provokes Women to transgress the Rules of common Modesty, without restraint.
However, a slightly earlier medical dictionary also mentions furor and expatiates on the "strange Distemper" of furor uterinus. From Stephen Blancard, The Physical Dictionary: Wherein the Terms of Anatomy, the Names and Causes of Diseases, Chyrurgical Instruments, and Their Use, Are Accurately Describ'd, second edition (1693):
Furor, the same with Manea [defined under Mania as "a sort of Madness, a deprivation of Imagination or Judgment, with great Rage and Anger, but without a Fever and Fear. It proceeds from Sulphureo-Saline Animal Spirits, like Aqua stygia, which cause strange furious impulses in the Body, not by consent of Parts; but by their own Strength."].
Furor Uterinus, an unseemly Distemper, which is wont to seize upon Maids ; especially those of riper years, and sometimes Widows too. They who are troubled with it, throw off the Veil of common Modesty and Decency, and delight only in Lascivious, Obscene Discourses : They covet a Man greedily, and even furiously, and omit no inviting Temptations that may induce them to satisfie their desires. The cause seems to be in the Seminal Juice, which being exalted to the highest degrees of Maturity, drives the Maids into a kind of Fury ; which is conspicuous every Year in some Bruits ; as in Cats, Bulls, Bucks, Does, Harts. ...
The source of this analysis, according to Ephraim Chambers, Cyclopaedia: Or an Universal Dictionary of Arts and Sciences (1741) was Daniel Sennert, a German physician whose Nine Books of Physick and Chirurgy was translated into English in 1658. Nathan Bailey, Universal Etymological Dictionary, second edition (1724) has an entry for furor uterinus, but not for furor alone:
FUROR Uterinus, a Distemper which provokes Women to transgress the Rules of common Modesty. L.
Bailey's Dictionarium Britannicum: Or a More Compleat Universal Etymological English Dictionary (1730) does have entries for both terms:
FUROR, fury, madness, rage, L.
FUROR uterinus {with Physicians} i. e. the fury of the womb, a species of madness peculiar to women, exciting them to a vehement desire of venery, and rendering them insatiate therewith, L.
But the definition for furor uterinus that appears in his 1724 Universal Etymological Dictionary appears instead as the definition of nymphomania.
Most eighteenth- and nineteenth-century British English dictionaries have no entry for furor at all. Perhaps most surprisingly, furor doesn't appear in editions of Samuel Johnson, A Dictionary of the English Language, from the first edition (1755) to the ninth edition (1806), nor in H.J. Todd's two revisions of Johnson's Dictionary—the first edition (1818) and the second edition (1827), indicating that the word wasn't widely used in England from the middle decades of the eighteenth century until well into the nineteenth century. As late as 1881 an edition of John Walker's A Critical Pronouncing Dictionary, updated by Edward Smith, has nothing on furor or furore.
In the United States, Joseph Worcester, A Comprehensive Pronouncing and Explanatory Dictionary of the English Language (1830) has no entry for furor. The word does appear in Worcester's A Universal and Critical Dictionary of the English Language (1846), but Worcester puts it in italics:
FUROR, n. {l.} Fury; madness; rage. Sir T. Wyatt.
In a usage note at the front of this dictionary, Worcester remarks, "Words printed in Italics, in the Vocabulary are words which belong to foreign languages, and are not properly Anglicized."
The earliest Webster’s dictionary to include an entry for furor seems to be An American Dictionary of the English Language (1847):
FUROR, n. {L.} Fury ; rage.
The 1864 edition of An American Dictionary of the English Language only slightly alters the entry:
FUROR, n. {Lat. from furere, to rage. Cf. FURY} Fury ; rage.
The breakthrough occurs with Webster's International Dictionary (1890), which has these entries:
Furor, n. {L. Cf. FURY} Fury ; rage.
Furore, n. {It.} Excitement; commotion; enthusiasm.
I can't replicate the pronunciation symbols that this dictionary uses, but it specifies that furor is a two-syllable word pronounced "fu´-ror," while furore is a three-syllable word pronounced "foo-ro´-ra."
A scant 19 years later, however, Webster's New International Dictionary (1909) reported the merging of the two words and their meanings in the single spelling furor:
furor, n. {L. : cf. F. fureur, OF. also furor. Cf. FURY.} 1. Fury ; rage ; also, madness or mania ; sometimes, specif., the "frenzy" or "enthusiasm" of poets or inspired persons. 2. A public or contagious enthusiasm or excitement ; esp., a prevalent and excited admiration ; a "rage" ; a "craze."
That was quick. As of 1909, we have all but one of the meanings that appear in the Eleventh Collegiate Dictionary (noted at the start of this answer). The exception is the "furious or hectic activity/outburst of indignation: uproar" meanings that appear as definitions 4a and 4b there.
Changing entries for 'furor' and 'furore' during the past 100 years
An entry for furore reappears in Webster's Fifth Collegiate (1936), along with an entry for furor:
furor n. 1. Fury; frenzy. 2. Poetic or religious enthusiasm. 3. A prevalent and excited admiration; a "rage" a craze.
furore n. Furor; a "rage."
According to this dictionary the pronunciation of furor is "fū´-rôr" and the primary pronunciation of furore is "fū´-rōr"—although it also lists a three-syllable pronunciation of furore that is similar to the one that appeared in the 1890 Webster's International.
The next change comes with the Seventh Collegiate (1963):
furor n 1 a : ANGER, RAGE b archaic : a state of fervent inspiration : FRENZY 2 : FURORE
furore n 1 : a contagious excitement; specif : a fashionable craze 2 : a public disturbance
This dictionary gives a pair of two-syllable pronunciations for both words, in reverse order: "'fyu̇(ə)r-ȯ(ə)r" and "'fyu̇(ə)r-ō(ə)r" for furor, and "'fyu̇(ə)r-ō(ə)r" and "'fyu̇(ə)r-ȯ(ə)r" for furore. The three-syllable pronunciation of furore is gone—but it returns as a third pronunciation ("esp Brit") in the Eighth Collegiate (1973) a thoroughly revamped set of definitions for the two words that has remained unchanged through the most recent (2003) Eleventh Collegiate.
The "outburst of indignation" sense of furor and furore has been lurking at the periphery of the "commotion" meaning of furor/furore since 1890, but Merriam-Webster didn't identify it as a distinct sense of the word until 1963.
Contextual note: 'furor' as madness during the period 1700–1900
As I suggested in the first part of my answer, furor had a specifically medical/psychological meaning for more than 200 years, and that meaning seems to have been considerably more common than any competing meaning in English texts. Very early instances of the word use it in the sense of anger or rage, as is the case with Henry Howard, "Complaint of the Absence of His Love" (by 1547), in Poems of Henry Howard, Earl of Surrey, Who Flourish'd in the Reign of Henry the Eighth (1717):
And yet with more delight to moue my wofull case,/ I must complaine these hands, those armes, that firmly do Embrace./ Me from my selfe, and rule the sterne of my poor lyfe,/ The sweet disdaynes, the pleasant wrathes, and eke the louely strife./ That wonted well to tune in temper just and mete,/ The rage, that oft did make me Err by furour vndiscrete.
But a Google Book search results from about 1700 forward shows a preponderance of instances of furor in the sense of mania or passion.
From Jonathon Swift, “A Discourse Concerning the Mechanical Operation of the Spirit” (1704):
I think, it is agreed among physicians, that nothing affects the head so much, as a tentiginous humour, repelled and elated to the upper region, found by daily practice to run frequently into madness. A very eminent member of the faculty assured me, that, when the quakers first appeared, he seldom was without some female patients among them for the furor—persons of a visionary devotion, either men or women, are in their complexion of all others the most amorous: for zeal is frequently kindled from the same spark with other fires, and, from inflaming brotherly love, will proceed to raise that of a gallant.
From Thomas Brown, Letters from the Dead to the Living, Part 2 (1707)
A Noble Peeress, that lives not full a Hundred Miles from St. James's-Square, in the Sixty fifth Year of her Age, was seiz'd with a Furior Uterinus ; By plying her Ladyship with a few Drops of my Antepyretical Essence, extracted from a certain Vegetable gather'd under the Arctic Pole, and known to no body but my self, I perfectly allay'd this preternatural Ferment ; and now she lies quiet, tho’ both her Hands are untied, as a new swaddled Babe, and handles no Raskals but Pam, and his Gay Fellows of the Cards.
From a review of Kristni-Saga, in The Monthly Review, or, Literary Journal (January 1776):
The first gives an account of the Berseki: a kind of bruisers, in ancient times, who were seized, by intervals, with the wildest furor; during which they plunged themselves into the greatest dangers, and committed the most horrid outrages. They are frequently mentioned in the monuments of Northern antiquity. These fits of madness, which seized them on a sudden, were soon over; but during such a paroxysm, their strength is said to have been more than human; and that not even fire, if we can believe it, nor any weapon, could hurt them.
From a review of Drury’s Illustrations of Natural History, in The Monthly Review (July 1783):
The Norway rats are so numerous and so bold, that they will come and feed by the side of the table at supper, and during the still hours of the night, search every corner for plunder, making a continual uproar, and often, in a kind of furor, carry away small utensils, and other articles, which they can turn to no advantage either for food or shelter. They are very mischievous to the naturalist's collection of plants and feeds, tearing them, and the books in which they are kept, in pieces, as it were in wantonness, and carrying away such as are edible, in which they are assisted by the land-crabs.
This last instance is notable as being one of the earliest one (aside from Henry Howard's, from the first half of the sixteenth century) that my Google Books searches turned up in which furor is not italicized as a foreign word. Besides these instances, there are numerous references between 1686 and 1908, especially in the latter half of the nineteenth century, to furor uterinus in a strictly medical sense, as well as other diagnosed furors.
'Furore'—and similar senses of 'furor'—in the wild
My 1971 edition of the Oxford English Dictionary cites Thomas Carlyle in 1851 as providing its first occurrence of furore:
furore Enthusiastic popular admiration ; a ‘rage’, ‘craze’.
[Cited examples:] CARLYLE in Froude Life (1884) II. 83 This blockhead .. is ..making quite a furore at Glasgow. 1864 LEWINS H. M. Mails 263 It was little thought that .. they would excite such a furore among stamp collectors. 1867 DICKENS Lett. 25 Nov., If we make a furore there.
Carlyle's remark occurred in the context of a letter (dated September 10, 1851) in which he discusses an Italian lecturer in the neighborhood of Scotsbrig, Dumphries (where Carlyle was then staying):
Father Gavazzi is going to harangue them [at Dumphries] to-morrow in Italian, which one would think must be an extremely unprofitable operation for all but the Padre himself. This blockhead, nevertheless, is actually making quite a furore at Glasgow and all over the west country, such is the anti-Popish humour of the people.
The William Lewins quotation is originally from "The Stamp Mania," in Chambers’s Journal (June 6, 1863):
When postage-stamps were first introduced in England, it was little thought that they would become a medium of exchange, and far less that they would excite such a furore among stamp-collectors.
Here there is no circumstantial Italian angle to justify the choice of furore; still, the word appears in italics to signify its foreignness. The word goes unitalicized in the Dickens instance, which is from a letter he wrote in Boston on November 25, 1867, reprinted in The Letters of Charles Dickens, volume 2 (1880):
Communications about readings incessantly come in from all parts of the country. We take no offer whatever, lying by with our plans until after the first series in New York, and designing, if we make a furore there, to travel as little as possible.
It seems most probable that furore crept gradually into the consciousness of English speakers over several decades during which it sporadically appeared in the conversation or writings of persons who spoke Italian. Because two of the OED's earliest three cited instances involve private letters, the term seems unlikely to have burst into public use from those sources.
The use of furore to mean "commotion or uproar" seems to have occurred at very nearly the same time that furor acquired the same meaning. It bears repeating that furor was widely treated as a foreign word in English well into the nineteenth century and that—for much of its several centuries of prior presence in English—it was primarily a medical term with a similar meaning to mania, used especially in the term furor uterinus, which eventually gave way to the term nymphomania. An item titled “Santluss on the Conditions of Insanity in Men, and Their Bearing on Responsibility” in The London Medical Record (July 31, 1875) offers this graphic description of how furor and mania differ:
The distinction between mania and furor is shown by a story by Reil. A woman, during her pregnancy, has an incessant craving to eat the flesh of her husband. She kills him, and pickles him. The killing was the furor, the craving was the mania.
Furor in the sense of "negative uproar" occurs in "Where is the Man with the Ether?" in Journal of Zoöphily (June 10, 1910):
Another step was taken by the defenders of vivisection to divert the growing movement for regulation of the practice is the removal from public sale of all copies of the volume on "Surgical Shock," written by Dr. George W. Crile. This book, when it made its appearance in 1899, caused a furor of indignation, not only on the part of the general public, but also among medical men.
An article titled "High Finance in the Milk Trade," in The Pacific Dairy Review (January 6, 1910) contains an instance of furore as "negative uproar":
Back in New York city the advance in the price of milk to nine cents a quart has caused a great furore among the consumers, which finally resulted in an official investigation as to the existence of a "trust" that is able to fix prices.
Those consumers were clearly not expressing admiration at the price increase. Thirty years earlier, this instance arose in "Testimony of J. W. Cromwell" on January 19, 1880, in Proceedings of the Select Committee of the United States Senate to Investigate the Cause of the Removal of the Negroes from the Southern States to the Northern States (1880):
Q. What do you know, anyway, about this exodus?
A. ... I was surprised to find such a unanimity of feeling on the part of the conference in favor of emigration from the Southwest. There was a positive furore about it; so much so that some of the other business for which the conference was called could not be attended to.
...
You say there was a furore in that convention, or conference, on the subject of emigration; what was the origin or cause of that furore?
A. Well, it had its origin in the complaints of the colored people.
Here furore may be intended in the sense of "enthusiasm" or "popular excitement," but it can easily be read as well as involving "positive commotion" and "positive uproar"—and those notions are less distant from "negative commotion" and "negative uproar" than one might think.
At the same time, furor has sometimes appeared in the "popular admiration" sense, as it does in William Ostler, “Tuberculosis,” in A System of Practical Medicine, volume 1 (1897):
Tuberculin.—The announcement by Koch that he had obtained a material which exercised a specific curative action on a tubercle caused a furor of excitement never, perhaps, equalled in the history of medicine. At present we are deep in the reaction following the failure to substantiate that claim.
Again, this instance of furor seems to have much the same meaning as the instances of furore in the preceding example.
Conclusions
Here are my provisional answers to the three posted questions.
1. What (a book, a play etc.) made "furore" a term adopted by the English language in the late 18th century with a different connotation from its original one?
There was no breakthrough instance of usage that propelled furore into English—certainly not in 1790. It seems clear to me that furore introduced the "positive excitement or enthusiasm" and "fashionable craze" senses that furor later to some extent took over. But furor was itself an out-of-the-mainstream word during the 1700s and 1800s, so it isn't surprising that English speakers weren't clear about where the meanings of furor stopped and the meanings of furore began.
That furore rather quickly lost its original sense—or at least became fuzzy—is evident from this discussion in "The Italian Element in English" (1929):
Furore was coined by the same nation which first used the word voga (i.e., vogue) for 'a fashion': to make a furore translates the Italian far furore. The present use of the word in England seems to have slightly altered from its source. For instance in Aloysius Horn (The Ivory Coast in the Early Nineties, 1927, p. 38: "Writing’s always been a bit of a furore with me").
The alteration in this instance seems to involve the personalization of what is ostensibly a group phenomenon. But confusion between furor and furore had even more problematic aspects.
2. When, roughly, did its meaning "enthusiastic popular admiration" start to die out?
Although none of the dictionaries that I consulted agree that furore in the sense of "enthusiastic popular admiration" is obsolete, a Google Books search doesn't turn up any matches for furore in that sense from recent years. I suspect that widespread use of furore to mean "vogue, rage, craze, or fad" was actually rather short-lived, for several reasons.
First, Merriam-Webster's 1790 origin date notwithstanding, furore seems not to have achieved even limited popular usage until the 1820s (as detailed in my other answer to this question), and the "vogue" meaning was not well established before the competing "positive or negative public excitement or uproar" meaning began to catch on in the 1840s, confusing the issue of which meaning was intended. The earliest dictionary I've found that includes an entry for furore is Webster's International Dictionary from 1890. Second, the status and meanings of furor weren't well settled in popular English either, adding to the confusion surrounding furore. Third, multiple unambiguous alternatives for the "vogue" sense of the word were available—and English speakers and writers evidently took them.
3. Is "furore" currently used as a close synonym of "furor," or does it carry different nuances in BrE and AmE?
The dictionaries I cite earlier in this answer indicate that furore has two meanings, and that those meanings are identical to two of the five meanings that furor has. I'm not aware of any U.S. English speakers who treat furor and furore as having distinctly different meanings—although there must be some. In any event, most U.S. English speakers use furor to the exclusion of furore.
I can't speak to British English tendencies, other than to note that furore appears to be significantly more common in British English sources than in U.S. English sources. But whether some, many, or most British English speakers and writers consistently use furor and furore to signify different things, I do not know.