Green’s Dictionary of Slang

gammon v.

[? game v. (3) or SE (back)gammon or fig. tying up of a gammon or ham; NB ‘Sl. Terms & the Gypsy Tongue’ in Baily’s Mag. Nov. 1871 suggests origin in Hindi ghumana, to beguile]

1. to cheat (at a game).

[UK]B.E. Dict. Canting Crew.

2. (UK Und.) to help.

[UK]J. Poulter Discoveries (1774) 42: Will you gammon me; will you help me.
[UK]Whole Art of Thieving [as cit. 1753].

3. to talk criminal slang.

[UK]G. Parker Life’s Painter 180: Gammon and Patter. Jaw talk, etc. A fellow that speaks well, they say he gammons well, or he has a great deal of rum patter.

4. to deceive, to fool, to talk humbug, to pretend.

[Ire] ‘Swaggering Jack’ Luke Caffrey’s Gost 3: He gammoned the twelve and worked on the water, / But a pardon he got from his gracious King.
[UK]Vaux Vocab. of the Flash Lang. in McLachlan (1964) 242: gammon: To gammon a person, is to amuse him with false assurances, to praise, or flatter him, in order to obtain some particular end; to gammon a man to any act, is to persuade him to it by artful language, or pretence; to gammon a shop-keeper, &c., is to engage his attention to your discourse, while your accomplice is executing some preconcerted plan of depredation upon his property; a thief detected in a house which he has entered, upon the sneak, for the purpose of robbing it, will endeavour by some gammoning story to account for his intrusion, and to get off with a good grace.
[Aus]P. Cunningham New South Wales II 232: All these innocent rogues [...] laugh and vaunt most immoderately, when sitting among their comrades, how they have gammoned you over.
[UK] ‘A New Political and Reform Alphabet’ in C. Hindley Curiosities of Street Lit. (1871) 83: If they think to gammon us out of reform / They will find we’ll be gammoned no more.
[UK]‘Swished for a Week’ in Rake’s Budget in Spedding & Watt (eds) Bawdy Songbooks (2011) III 72: I next with onions rubbed my eyes / And gammon’ a lot of tears and sighs.
[Aus]Sydney Herald 18 June 4/2: [B]low me if it warn’t capital, you [...] gammoning the knowing ones till the Recorder almost gave in, and the lawyers almost returned the brads.
[UK]Flash Mirror 6: Gammoning or Magging. — Meeting a Yokel [...] persuading him to enter a public house with you, making him drunk [etc] .
[Ire] ‘A Week’s Matrimony’ Dublin Comic Songster 293: I next with onions rubbed my eyes, / And gammoned a lot of tears and sighs.
[Aus]Satirist & Sporting Chron. (Sydney) 25 Mar. 4/1: I think you are gammoning me, or I would tell you in quick sticks.
[Aus]Bell’s Life in Sydney 31 Jan. 2/5: [...] those on whose charity he practised by gammoning to be blind.
[US]‘Ned Buntline’ Mysteries and Miseries of N.Y. I 66: You’ve been awfully gammoned.
[UK]‘Ducange Anglicus’ Vulgar Tongue 39: Fawney droppers gammon the flats and take the yokels in.
[UK]Leaves from Diary of Celebrated Burglar 26/2: I’ll bet a ‘quid’ that he ‘gammons’ the ‘fawney’ from her, besides.
[Aus]Wkly Times (Melbourne) 2 Aug. 9/5: Some of this sort call theirselves ‘returned Australians,’ in London, and gammon to represent us in the little village.
[UK]Whitecross and the Bench 147: He gammoned the prison doctor here that he had a predisposition to fits.
[Aus]‘Rolf Boldrewood’ Robbery Under Arms (1922) 122: I see the swell chap first — him as made out he was the owner, and gammoned all the Adelaide gentlemen so neat.
[Aus]Truth (Sydney) 30 Dec. 4/6: Workmen were busy gammoning to superintendants certain vital principles of what knowing cards termed ‘the derned old humbug’.
[UK]Belfast Wkly News 21 Dec. 3/2: There’s a cove [...] who ‘gammons’ he’s a broken-down merchant and he’s got the gift of the gab so that he can make folks believe it.
[UK]Boy’s Own Paper 27 Nov. 133: I say it arn’t fair to try and gammon a lot o’ men as is ready to fight for you.
[Aus]J. Furphy Such is Life 230: He gammoned dead till we poured a pint of beer down his throat; and he lay groaning for two solid hours, winking now and then at Nelson.
[UK]Gem 16 Sept. 2: I-I suppose the kid isn’t gammoning us.
[Aus]G.H. Lawson Dict. of Aus. Words And Terms [Internet] GAMMON—To deceive.
[Aus]W.E. Harney Brimming Billabongs 7: Let’s gammon we are old men and talk big.
[US]J. Greenway ‘Australian Cattle Lingo’ in AS XXXIII:3 166: gammon, To fool around.
[Aus] in K. Gilbert Living Black 291: Don’t listen, they gammon.

5. to persuade.

[UK]Egan Life in London (1869) 310: In consequence of Bob’s plausibility, I was gammoned to be one of the squad.
[UK] ‘Moses Samuals And The Nasty Little Vomans’ in Secret Songster 10: And den at last she gammon’d me to go vith her to bed.
[UK]J. Lindridge Sixteen-String Jack 118: ‘He is a hinnocent chicken we doubts,’ said Peter, ‘but let him gammon us to that at the Old Bailey.’.
[UK]A. Mayhew Paved with Gold 155: I wish I could gammon you to take a fiver for it [i.e. a ratting dog].
[UK]C. Hindley Life and Adventures of a Cheap Jack 69: if he could good-humouredly gammon him out of the company he would, but if the cove showed the least inclination to go by persuasion, the fat man would use such force that few [...] could stand up against.
[UK]Sporting Times 3 Jan. 2/2: I gammoned him that jim-jams might go into lunacy.

6. to tease amicably.

[UK]Dickens Pickwick Papers (1999) 174: They pours him out a glass o’ wine, and gammons him about his driving, and gets him in a reg’lar good humour.

7. (UK und.) to hold a horse while its rider is elsewhere, i.e. in a shop, visiting a friend.

[UK]Flash Mirror 6: Coaxing a Trotter. — Togging as a cove that gammons (holds) the horses at the west end of town.

8. to flatter.

[NZ]Grey River Argus (NZ) 24 Aug. 2/6: I’m sorry to say as ’ow she’s prowd — werry prowd, all along o’ them there swells as gammons her up and calls her a votehairy.

9. (Aus./Qld) to fool around.

[Aus]Aus. Word Map [Internet] gammon around to fool around.

In phrases

gammon the draper (v.)

‘When a man is without a shirt, and is buttoned up close to his neck, with merely a handkerchief round it, to make an appearance of cleanliness, it is termed, “gammoning the draper”’ (Egan, Life in London, 1821).

[UK]Egan Life in London (1869) 221: Mahogany Bet, has been chaffing Spendall [...] about his being so cucumberish as to be compelled to gammon the draper.
gammon the twelve (in prime twig) (v.) [SE twelve, generic for the jury + in fine twig under twig n.1 ]

(UK Und.) to gain an acquittal in court; the implication is that the defendant has managed to fool the jurymen.

see sense 1 above.
[UK]Vaux Vocab. of the Flash Lang. in McLachlan (1964) 243: gammon the twelve a man who has been tried by a criminal court, and by a plausible defence, has induced the jury to acquit him, or to banish the capital part of the charge, and so save his life, is said, by his associates to have gammoned the twelve in prime twig, alluding to the number of jurymen.
[UK]Egan Grose’s Classical Dict. of the Vulgar Tongue.
[UK]Egan Finish to the Adventures of Tom and Jerry (1889) 149: He could not ‘gammon the Twelve,’ as to his innocence; and they [...] placed him under the protection of His Majesty’s Government, to study Botany for the remainder of his life.