Green’s Dictionary of Slang

1. a decoy.

c.1863		gloss. in Occurence Book of York River Lockup in Seal (1999) 38: I want a stalsman buttoner to nail prads.
1901		W.A. Sun. Times (Perth) 28 July 1/1: A sweet brunette was the decoy duck in the remunerative conspiracy [...] the beauteous ‘buttoner’ wheedled £150 out of the amorous dotard.
1908		Truth (Brisbane) 12 Apr. 9/3: But the wust of all them pushers / Are the klnchin buttoners / Who goes trailin round the streets / [...] / For to lay the magsman on. or / Burrow out a easey mug.

2. the member of a gang running a any form of criminal gambling, e.g. three-card monte n., who persuades passers by to bet on the inevitably fraudulent game.

1839		H. Brandon Dict. of the Flash or Cant Lang. 161/2: Buttoner – one who entices another to play.
1841		Blackwood’s Mag. L., 202: Buttoners are those accomplices of thimble-riggers... whose duty it is to act as flat-catchers, or decoys, by personating flats [F&H].
1857		J. Archbold Magistrate’s Assistant (3rd edn) 446: To entice another to play – buttoner.
1865		Leaves from Diary of Celebrated Burglar 8/1: An immediate opening is made and the ‘flat’ is inclosed and surrounded by the ‘buttoners,’ who [...] ‘kid’ the ‘flat’.
1870		Hotten Sl. Dict.
1882		Sydney Sl. Dict. (2 edn) 2: Buttoners - Assistants of stage tricksters who mingle with the audience.
1894		Truth (Sydney) 23 Sept. 6/5: In the bright lexicon of the ‘buttoner’ there is a proverb to the effect that ‘a Mug is born every minute’.
1900		Bulletin (Sydney) 8 Dec. 20/4: [A]t every table Mr. Jay visited – whether the attaction was cards, dice, marbles, or ‘Spinning Jenny’ – the owners thereof looked sideways at him with a curiously shamefaced air, as though they mutely apologised for the crude simplicity of their little swindles, and the ‘buttoners’ slunk away from him.
1900–10		Stephens & O’Brien Materials for a Dict. of Aus. Sl. [unpub. ms.] 36: BUTTONER [...] the confederates of ‘gees’ / assistants who ‘gee up’ the mugs / of roulette, hazard, thimble-rigging or other ‘spielers’. Possibly from ‘buttonholing,’ a method of holding a man by the coat lapel while you strive to talk or do business with him.
1907		Sun. Times (Perth) 11 Aug. 4s/8: The scum of Hunter’s Corner gang / [...] / The buttoners, touts and runners.
1910		Sun. Times (Perth) 24 July 2nd sect. 10/6: The punter in question [...] came wandering up the Terrace in quite a casual sort of manner, accompanied by a couple of acquaintances, who afterwards turned out to be ‘buttoners’ for him.
1920		C. Drew ‘The Smokeroom’ in Referee (Sydney) 28 Jan. 14/6: A crowd of men closed in on him, Snatcher's buttoner grabbed the ticket.
1977		D. Powis Signs of Crime 176: Buttoner Assistant in three-card trick ‘firm’ who brings customers to the game, and thus any bringer of dupes to a fraud.
1999		G. Seal Lingo 146: spieler, meaning a swindler, often a cardsharp, was common among circus people and other travelling entertainers by the 1870s. It was joined in the following decade by buttoner, a person who assisted show people by encouraging volunteers to come forth from the audience. Both these words seem to derive from British circus usage.

3. in ext. use, referring to any crooked businessman.

1883		Grey River Argus 20 Sept. 4/1: I am afraid he is acting the part of a bank buttoner if he does not publish the mint report.
1885		Bulletin (Sydney) 25 Apr. 11/1: Slowly, but surely, British civilization is doing its usual philanthropic work up North, and the time is evidently close at hand when ‘that furred tongue, bad-tasting mouth, and miserable feeling’ will be as common amongst our black brudders as they now are amongst our distinguished senators, land-sale buttoners, and race-reporters.
1901		W.A. Sun. Times (Perth) 21 Apr. 1/1: The Gas Co.’s ‘buttoners’ were visibly affected at the rejection of the ancient Allison.
1914		Truth (Melbourne) 10 Jan. 4/2: As the buttoners [i.e. mock auctioneers] had the game all to themselves, they very quickly got tired of the sport.

4. in non-criminal use, an advocate.

1908

Sun. Times (Perth) 6 Dec. 1/1: An eminent journalist has constituted himself buttoner for the Wednesday-closing push.