Before World War II the word "holocaust" referred most often to a huge inferno. Who first used the term to describe the Nazi murder of 6 million Jews? When and where?
In the sense of ‘the mass murder of the Jews by the Nazis in the war of 1939–1945’, the OED says
The specific application was introduced by historians during the 1950s, probably as an equivalent to Hebrew ḥurban and shoah ‘catastrophe’ (used in the same sense); but it had been foreshadowed by contemporary references to the Nazi atrocities as a ‘holocaust’.
The earliest of those contemporary references is from this newspaper report in 1942:
Holocaust . . . Nothing else in Hitler's record is comparable to his treatment of the Jews . . . The word has gone forth that . . . the Jewish peoples are to be exterminated . . . The conscience of humanity stands aghast.
---News Chronicle, 5 December 1942, UK
John Ayto, Dictionary of Word Origins (1990), notes instances in English long before World War II in which holocaust referred not merely to "a huge inferno" but to a slaughter:
Etymologically, a holocaust is a 'complete burning,' and the word was originally used in English for a 'burnt offering,' a 'sacrifice completely consumed by fire' (Mark 12, 33, 'more than all whole burnt offerings and sacrifices' in the Authorized Version was translated by William Tindale in 1526 as 'a greater thing than all holocausts and sacrifices'). ... John Milton was the first English writer to use the word in the wider sense 'complete destruction by fire,' in the late 17th century, and in the succeeding centuries several precedents were set for the modern application to 'nuclear destruction' and 'mass murder' — Bishop Ken, for instance, wrote in 1711 'Should general Flame this World consume ... An Holocaust for Fontal Sin,' and Leitch Rithie in Wanderings by the Loire 1833 refers to Louis VII making 'a holocaust of thirteen hundred persons in a church.'
For a sense of how surprisingly slowly the shoah sense of holocaust came to dominate all other meanings of the term in the post-World War II era, consider this complete entry in Evans and Evans, A Dictionary of Contemporary American Usage (1957):
holocaust; disaster. A holocaust is a Greek word meaning something which is burnt whole. It was used for a burnt offering and has come to mean, especially in journalistic writing, a great or wholesale destruction of life, especially by burning (Incendiary bombs led to a holocaust in the slum quarter). Holocaust is often used as a synonym for disaster, but there is a difference: a holocaust may be a disaster, but there are many kinds of disasters which are not holocausts. Disaster (which means literally a bad configuration of the stars, i.e., just bad luck) designates any unfortunate event, especially a sudden and great misfortune. A holocaust may be accidental, but it may also be the result of human intention. A flood, a railway wreck, or the collapse of a building may be a disaster, but none of these things is a holocaust.
And here is a second (and even later) complete example, from Morris and Morris, Dictionary of Word and Phrase Origins (1962):
holocaust Holocaust (pronounced HOL-oh-kost) is a word we sometimes see in the headlines, yet it is not one that many of us find in our speaking vocabularies. Originally a holocaust was a sacrificial burnt offering to pagan gods in pre-Christian times. It is derived from the Greek words holos (whole) and kaustos (burnt). Nowadays it is generally used to mean slaughter and destruction on a very wide scale, especially by fire, as in the sentence: "All London was a holocaust after the bombers left."
It is unimaginable that a serious reference work written today would discuss the term holocaust without specifically mentioning the Nazi-orchestrated shoah at some point.
The "coined ... holocaust" question above is immediately followed by an untrue assertion:
“Before World War II the word "holocaust" referred most often to a huge inferno.”
The "h" word had a wide range of referents during the 1930's; "a huge inferno" was a possible but not an often encountered meaning.
A word search of the New York Times index for the three year period starting January 1936 turns up 64 employments — about two "holocausts" a month. Below the first five of 1936:
...'Funeral March for the Last Scene of Hamlet,' a piece eminently suited to the atmosphere resultant from the holocaust to which that something rotten in the state of Denmark led." [March 22]
"... one of the worst droughts ... To make up some of the ravages of this holocaust, we brought in from abroad some feedstuffs and other agricultural products urgently needed ..." [May 23]
"... 6,000 British seamen died in Jutland's brief holocaust of flame and smoke." [Reference is to the major World War I naval battle.] [May 31]
"... the intolerable sufferings of the millions of Jews in 'the European holocaust.’"
And from the text of the petition within the article:
"Bold practical measures to save those unfortunate millions from total annihilation are now called for ... Great Britain has it within her power to throw open the gates of Palestine and let in the victimized and persecuted Jews escaping from the European holocaust." [May 31]
- “Bootleg Fireworks: ...the noise and destruction will increase in volume until the second Saturday, when the holocaust will reach its height, and then in a last week it will slowly fade and die for another year." [June 11]
I suggest the "h" word occurred to many minds independently as one of a range of possible referents to the Jewish experience in Nazi dominated Europe, that the word was not "coined" in the sense of "invented" or "devised" by one individual or authority as the title question "who coined ..." implies.
And it should be noted that today's users of the words "the Holocaust" disagree or are simply fuzzy as to whether Nazi persecution of Jews in the 1930's are to be considered part and parcel of "the Holocaust" and also significantly disagree (or are fuzzy) as to who exactly, beyond Jews, were Holocaust victims. (Yad Vashem, the Israeli Shoa/Holocaust memorial museum, and the first centre of what is now known as "Holocaust Studies" usually defines 'the h/Holocaust' as the persecution and murder of Jews 1933-1945 within Nazi controlled territory.)
A few significant employments of "holocaust" 1933-1942 referencing persecution and/or mass murder of Jews in Nazi ruled Europe follow — (also see the May 31 1936 "European holocaust" quotes from the New York Times above):
Else Lasker Schuler, the poet, one of a number of prominent German Jews reported to have disappeared without a trace, is alive and safe ... Dr. Margoshes said he had received a letter from the poet at Zurich ... stating that 'she had run away from the the holocaust' and was destitute but perfectly safe."
New York Times, 1 June 1933, p 6:8 — probably the earliest well circulated American 'the holocaust' referencing Nazi persecution of Jews. Hitler was appointed German chancellor in January 1933, assumed dictatorial powers in March and in April most Jews in government jobs were dismissed. Mass murder of Jews began in 1941.
The inflammatory fever which has been consuming Germany in recent years threatens a holocaust, a wholesale incineration ... The progress of the sickness can be examined in ... Mr. Warburg's account of racial persecution [of Jews]."
Times Literary Supplement (London), 26 August 1939, Philip Tomlinson, "Flamens" (lead article), p. 503:2. Britain declared war on Germany 3 September 1939.
"BEFORE THE HOLOCAUST" (The American Hebrew, 3 October 1941, front cover -- uppercase caption below a photograph of two men carrying Torah scrolls through a gate topped by a Mogen David. One of the men is wearing a Jewish prayer shawl, the other is dressed in a French uniform. France was invaded by Germany in May 1940.)
"This issue of the JEWISH FRONTIER attempts to give some picture of what is happening to the Jews of Europe ... In our calculations of the holocaust that has overtaken the Jews ... [w]e speak ... of the victims not of war, but of massacre ... The annals of mankind hold no similar record of organized murder."
Jewish Frontier, November 1942, editorial, p 3.
Probably, the first well circulated "holocaust" referencing the Nazi extermination campaign and employed by a writer with some real understanding of what was happening to the Jews of Europe -- authoritative news of systematic mass murder of Jews reached the English speaking world in the fall of 1942.
The OED (the unabridged Oxford English Dictionary) entry for "holocaust" is cited in one of the answers above. The OED's entry for "holocaust" is notably poorly organized, incomplete, and misleading. Dictionary definitions are often flawed and should not be relied upon for understanding how a word was employed at a particular time — word searches in the New York Times's index and similar often quickly give a better understanding of usage than a dictionary's definition.
No indication is given within the OED "holocaust" entry that the word, in the early 1960's, before it became the readily understood referent to the Jewish catastrophe of the Nazi period, was the common referent to feared nuclear destruction. (In a ten day period in July 1963 the New York Times employed the word in its nuclear sense five times -- 5 July 1963, p. 8:3; 6 July, p. 14:3; 9 July, p. 30:5; 11 July, p. 4:3; 15 July, p. 12:1).
And the OED entry, while giving examples of usage referencing 'authorized' Judeo/ Christian whole burnt religious offerings fails to clearly indicate that "holocaust" has seen significant employment referencing blasphemous/ heretical/ sacrifices to an idol or false god:
"... they haue forsaken me ... they haue filled this place with the bloud of innocents. And they haue built the excelses [high places] of Baalim, to burne their children with fire for holocaust [in the Hebrew OLOT] to Baalim: which I commanded not, nor haue spoken of, neither haue they ascended into my hart."
Rheims Douai Bible, 1582-1610, Ieremie [Jeremiah] 19:4,5.
Note the above is the only employment of "holocaust" to refer to the killing/ sacrifice of human beings (plural) in the Catholic Bible and that in Protestant Bibles the "h" word is essentially never seen — the words "burnt offering(s)" are employed to translate the Hebrew OLAH (OLOT).
Shoah scholars until around 2000, when commenting on the "h" word, often insisted that the word had strong Judeo/ Christian sacrificial connotations, totally ignored its pagan sacrificial employment, and implicitly claimed that the word had had little circulation in any secular, non-religious, senses before the word was adopted to reference the Jewish catastrophe.
(One Holocaust Studies article, reprinted and quoted by Shoah academics, asserts that "holocaust" was employed extensively in the King James Bible --- but the word is not to be found in that Bible. The introduction that appeared in early printings of the King James Bible states that "Papist" words such as "holocaust" have been avoided in the translation.)
A significant well circulated 'religious' employment of "holocaust" that has never been referenced, to my knowledge, by any Shoah scholar:
For him [Eli Wiesel] ... God is dead ... the God of Abraham, of Isaac, of Jacob ... has vanished forevermore ... in the smoke of a human holocaust exacted by Race, the most voracious of all idols."
(Francois Mauriac's introduction to Wiesel's Night, 1960).
Mauriac received the Nobel for literature in the 1950's, Wiesel picked up a Nobel for peace in the 1980's. According to the New York Times, ten million copies of Night had been sold by 2008 [see Rachel Donadiojan NYT book review of Night, 20 Jan 2008].
(Post 2006 printings of Night employ a different translation of the 1958 Mauriac and Wiesel French texts and this new translation has slightly different words before and after Mauriac's "human holocaust" than those of the above quoted 1960 edition.)
Wiesel's first use of "holocaust" to reference Nazi crimes was in August 1963 (" One finds this ... even in fiction whose theme has nothing to do with the Nazi holocaust. For example, in Fail Safe, the best seller about an atomic accident.")
Wiesel unfortunately has claimed authorship of "H/holocaust" in its current dominate sense: "I am the one who introduced the word into this framework." Some academics circulate a watered down version of this Wiesel statement. One academic paper asserts that the New York Times of 15 October 1986 — and unnamed other newspapers — credited Wiesel with "coining of the term." No "coining of the term" suggestion is to be found in the New York Times of October 1986.
Some notable American employments of "H/holocaust" in its current dominant sense in the 18 months before Wiesel's first employment:
... Counsel Says Mercy Might Help Avert New Holocaust [headline]"; "Eichmann ... might ... serve as an instrument against any recurrence of a Nazi holocaust." And "[The Attorney General of Israel stated]: 'the overwhelming majority of this country [identify] with the victims of the holocaust ...'"
New York Times, 24 March 1962, p. 7, col. 1.
And if the Jews outside Israel had to be shown the difference between Israeli heroism and Jewish submissive meekness, there was a complementary lesson for the Israelis; for 'the generation of Israelis who have grown up since the holocaust'..."
(Hanna Arendt quoting Ben-Gurion, New Yorker, 16 February 1963, p. 42)
The Dignity of the Destroyed: Towards a Definition of the Period of the Holocaust
(Essay title: Shaul Esh, Judaism, 1962, p. 99.)
"Miss Arendt Surveys the Holocaust" (Essay title: Marie Syrkin, Jewish Frontier, May 1963 - printed on the cover of the magazine in bold letters.)
The above presentation relies heavily on Jon Petrie's web essay on the word "h/Holocaust" and the essay's appendix critiquing the OED's "holocaust" entry. For that essay google search >Petrie word holocaust<. Warning: some of the writing in the Petrie essay and its appendix is dense, turgid.