Green’s Dictionary of Slang

gambler n.

[Johnson, Dictionary (1755), cites it as ‘a cant word, I suppose, for...gamester’ and defines it as ‘a knave whose practice it is to invite the unwary to game and cheat them’. The cheating inference had worn off by early 19C; even so, the modern professional gambler is assumed to depend on skill, albeit honest, rather than on luck]

1. a confidence trickster who drops a supposedly valuable object, e.g. a ring, a wallet, and rather than claim it for himself, persuades a passer-by to buy it from him.

[UK]Proceedings Old Bailey 2 July 88/1: The Prisoner has been a Gambler [...] for several Years past. [...] [note] A Gambler is one of the Modern Cant Names for a Money Dropper.
[UK]Bailey Universal Etym. Eng. Dict. n.p.: gambler, a guinea-dropper; one class of sharpers.
[UK]Proc. Old Bailey 11 Oct. 149/2: I heard nothing of him 'till he was taken as a Gambler, (or Money Dropper) the Tuesday following [...] He being taken on Tuesday for Gambling, he sent Mr. Bushel, an Apothecary in St. Paul's Church-yard, to the Compter with me.

2. a cheating card- or dice-player.

[UK]Grose Classical Dict. of the Vulgar Tongue.
[UK]Lex. Balatronicum.
[UK]Egan Grose’s Classical Dict. of the Vulgar Tongue.

SE in slang uses

In compounds

gambler’s roll (n.)

see under roll n.