Green’s Dictionary of Slang

1. (UK Und.) a pickpocket or cut-purse.

1591		Greene Second Part of Conny-Catching in Grosart (1881–3) X 107: The Foist is so nimble handed that hee exceeds the iugler for agility, and hath his legier de maine as perfectly : therfore an exquisite Foist must haue three properties that a good Surgion should haue, and that is an Eagles eie, a Ladies hand, and a Lyons heart: an Eagles eie to spie a purchase, to haue a quicke insight where the boong lies, and then a Lyons heart not to feare what the end will bee, and then a Ladies hand to be little and nimble, the better to diue into the pocket. These are the perfect properties of a Foist.
1600		J. Day Blind Beggar of Bednall-Green Act I: Your nipper, your foyst, your rogue, your cheat, your pander, your any vile thing.
1611		Middleton & Dekker Roaring Girle V i: Foist! what’s that? mol.: A diver with two fingers, a pickpocket.
1630		J. Taylor ‘Travels of Twelve-pence’ in Works (1869) I 71: To Sharkes, Stales, Nims, Lifts, Foysts, Cheats, Stands, Decoyes / T’a Cut-purse, and a pocket picking Hound.
1654		Mercurius Fumigosus 22 25 Oct.–1 Nov. 187: Of Gally-Foysts, and water Speeches, / Of Horn-fair Beasts in Sattin Breeches.
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue n.p.: Foyst, a pickpocket, cheat, or rogue. [Ibid.] A foyster was a pickpocket.
1811		Lex. Balatronicum.
1822		Life and Trial of James Mackcoull 299: She said she was no foyst, and was innocent.
1867		(con. 1600s) M. Lemon Leyton Hall I 233: The man that stood beside thee is old Crookfinger; the most notorious setter, barnacle, and foist in the City.

2. (UK Und.) a card-sharp, a cheat.

1598		Jonson Every Man in His Humour IV vii: Prate again, as you like this, you whoreson foist, you.
1608		Dekker Belman of London E3: Foysting : which is nothing else but a sleight to carry Dice easily in the hand so often as the Foister listeth.
1659		Greene & Lodge Lady Alimony V iii: You shall play no more the sharking foist with me, you fumbling Fidler you.
c.1698		B.E. Dict. Canting Crew n.p.: Foyst c. a Cheat a Rogue.
1725		New Canting Dict. [as cit. c.1698].
1737, 1759, 1760, 1776		Bailey Universal Etym. Eng. Dict. [as cit. c.1698].
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.
1822		R. Nares Gloss. (1888) I 320: Foist meant also a sharper, and is, perhaps, derived from to foist, in the sense of to thrust in improperly, which is said to be from fausser, French.
1859		Matsell Vocabulum.

3. a trick, a hoax.

1627

J. Taylor An Armado in Works (1869) I 85: The Friend-ship had two very small pinnaces in her squadron, named, [...] 2. The Foyst.