Green’s Dictionary of Slang

jawbreaker n.

also jawcracker, jaw-twister

1. a word that the speaker considers so long or complex that its pronunciation threatens to be harmful; thus jawbreaking, incomprehensible, unpronounceable; jawcrackery, the use of such terms.

[UK]Morn. Post (London) 22 Dec. 3/4: I know the mob delighted with jaw-crackery.
[Ire]S. Lover Legends and Stories 240: Such a jaw-breaker and peace-breaker as transubstantiation.
[US]Congressional Globe 29 Apr. 367: The gentleman had brought up many hard words, which he said he could scarcely spell, nor pronounce [...] They were in fact what in Virginia they termed ‘jawcrackers.’.
[US]‘Jonathan Slick’ High Life in N.Y. II 102: They called every thing by some darn’d jaw-breaker of a name. [Ibid.] 176: ‘What’s his name?’ sez Mr. Tyler. ‘Wal,’ sez I, ‘I eenamost forgot, but it’s a downright jaw-cracker – as long as a sarmon and as crooked as a corkscrew.’.
[US]F.M. Whitcher Widow Bedott Papers (1883) 106: I don’t admire double names any way, especially such awful jaw-breakers as that.
Elgin Courant (Moray, Scot.) 11 July 7/5: Whoy [sic] them’s the lads [...] hould palavers on ’em, and gie them reg’lar long jaw-cracker cognomens.
[UK](con. 1840s–50s) H. Mayhew London Labour and London Poor I 15/1: The high words in a tragedy we call jaw-breakers, and say we can’t tumble to that barrikin.
[UK]Western Times 17 Aug. 8/4: Z is for Zwilchenburt — what a jaw-breaker!
[UK]Luton Times 7 Sept. 2/7: ‘I schemlandamourtchwager you’ is said to be, so far as the jawbreaker is concerned, American indian for ‘ love you’.
[UK]Sl. Dict. 202: Jaw-twister a hard or many-syllabled word. Elaboration or preceding.
[US]C.F. Lummis letter 5 Nov. in Byrkit Letters from the Southwest (1989) 68: Not to mention the countless Spanish jawbreakers.
Leeeds Times 19 Dec. 5/3: His very name, even, is a jaw-cracker.
[US]H.F. Wood ‘Justice in a Quandary’ in Good Humor 179: He’s swallowed a lone dictionary and crammed down jawbreakers fit to bust him.
[US]Ade People You Know 32: He was burning the Midnight Oil and grinding out Jaw-Breakers, so as to qualify for the Master’s Degree.
[NZ]N.Z. Truth 30 Jan. 5/1: The glorious blooms [...] are prosaically tagged with jawbreaking Latin names.
[US]J. London Smoke Bellew (1926) 71: I can sure read and spell, an’ I know that Chechaquo means tenderfoot, but my education never went high enough to learn me to spell a jaw-breaker like that.
[UK]Eve. Teleg. (Dundee) 23 Apr. 4/3: With a fine jaw-cracker of a language, such as he [i.e. a Welshman] uses every day.
[Ire]Joyce Ulysses 292: And then he starts with his jawbreakers about phenomenon and science and this phenomenon and the other phenomenon.
[US]H. Asbury Gangs of Chicago (2002) 352: His real name was Wajciechowski, a jawbreaker which was changed to Weiss soon after his family arrived in the United States.
[UK]S. Murphy Stone Mad (1966) 95: You gave them some jawbreakers that night.
[UK]A. Burgess Right to an Answer (1978) 110: You certainly speak English good for a native. Where did you get all them jaw-breakers?
[US]J. Stahl I, Fatty 148: The man was a dictionary of 25-cent jawbreakers.

2. [I](Aus.) one who writes in a heightened manner.

Cornwall Press (Launceston, Tas.) 10 Mar. 3/3: [I]f he writes a style somewhat peculiar [...] he is decried as a ‘jaw-breaker’.

3. attrib. use of sense 1.

[UK](con. 1930s) D. Behan Teems of Times and Happy Returns 72: An’ himself an’ Frank Behan usin’ big jawbreaker words that neither of them understand.
S.G. Esrati ‘Book Rev.’ Amazon.com [Internet] It also lacks an index and a guide to the reader on all the Arabic jaw-twister names scattered throughout the book.

4. (US, also jawbone breaker, jawbone doctor, jawbuster, jaw puller) a dentist.

[US]Hostetter & Beesley It’s a Racket! 229: jawcracker — Dentist.
[US]Howsley Argot: Dict. of Und. Sl. 27: jawbuster – a dentist.
[US]R.F. Adams Western Words (1968) 84: Jaw cracker — A traveling dentist who goes from place to place over the range to relieve cowboys of their pain, teeth, and money.
[US]in DARE III 107/2: Joking words [...] for a dentist) [...] Jawbreaker [...] Jawbone breaker [...] Jawbone doctor [...] Old jaw puller.