Loggerhead was an established term for blockhead by 1600. Shakespeare uses loggerhead or loggerheaded four times in his plays. From The Taming of the Shrew (by 1592):
Petruchio. Here, sir! here, sir! here, sir! here sir!/You logger-headed and unpolish'd grooms!/What, no attendance? no regard? no duty?/Where is the foolish knave I sent before?
From Romeo and Juliet (by 1595):
Capulet. Make haste, make haste. [Exit 1 Serv.]—Sirrah, fetch drier logs;/Call Peter, he will show thee where they are.
2 Servant. I have a head, sir, that will find out logs,/And never trouble Peter for the matter. [Exit.
Capulet. 'Mass and well said; A merry whoreson! ha,/Thou shalt be logger-head. — Good faith, 'tis day:
From Love's Labour's Lost (mid-1590s):
Biron. [To Costard] Ah, you whoreson loggerhead! you were born to do me shame.
From Henry IV, Part 1 (1597):
Poins. Where hast been, Hal?
Prince Henry. With three or four loggerheads, amongst three or four score hogsheads.
Earlier still is the term log-headed. From Richard Edwards, Damon and Pythias (1564):
Aristippus. ... What crying out, what cursing is there within of Carisophus,/Because he accused Damon to King Dionysius!/Even now he came whining and crying into the court for the nonce,/Showing that one Onaphets had broke his knave's sconce./Which strange name when they heard, every man laughed heartily,/And I by myself scanned his name secretly;/For well I knew it was some mad-headed child/That invented this name, that the log-headed knave might be beguiled.
The notion of being "at loggerheads" was earlier expressed in the phrases "to come to loggerheads" or "to fall to loggerheads." The first instance of this phrase, according to John Farmer & W.E. Henley, Slang and Its Analogues, volume 4 (1896)‚ which is the source of many of my references here—is from Charles Cotton, Scarronnides, Or, Virgil Travestie (by 1670):
The first place after this vagary/He lighted on was Dido's Dairy;/Whence he Æneas soon did spie,/Ord'ring his Highness Husbandry:/He took upon him as her Spouse,/And vapour'd like the Man o' th' House;/For all that time, as't came to pass,/In Quarrell high engag'd he was,/And ready in hi fumigation,/(As Histories do make relation)/To fall to Logger-heads, as't appears,/With a few sawcy Carpenters,/Who building were an House of Ease,/For Dido in necessities,/They would not follow his advice,/(As workmen still are overwise)/Which made him foam, and flirt out spittle,/Because they made the holes too little.
Abel Boyer, Dictionaire Royal: Anglois–Francois, volume 2 (1722) has this brief note about "to fall to loggerheads":
To fall to Loggerheads, (to go together by the Ears, to Fight)
And a number of subsequent dictionaries, including William Perry, The Synonymous, Etymological, and Pronouncing English Dictionary (1805), give this version:
To go or fall to loggerheads, to scuffle, to fight without weapons.
The first instance of "at loggerheads" that Farmer & Henley identifies is from an 1846 issue of [Punch]:
'F. M. the Duke of Wellington will let Mr. Punch have the earliest intimation of anything definite being come to.' As we have not heard from his grace. ... we can only presume that the ministers were up to the last moment at loggerheads.
The phrase also arises in Anne Baker, Glossary of Northamptonshire Words and Phrases (1854):
LOGGERGEAD. A blockhead. [Quotation from George Farquhar, Sir Henry Wildair (1701), omitted]
- When relatives are disagreeing over property or other things, it is frequently said "they are all at loggerheads together." [A different quotation from Farquhar, Sir Henry Wildair, again omitted; it involves the phrase "fall to loggerheads," not "at loggerheads."]