Green’s Dictionary of Slang

1. to pick pockets, using the fore and middle fingers, extended like the tines of a fork, which are thrust into the pocket, then closed tight on any object within; this is then withdrawn between the ‘fork’.

c.1698		B.E. Dict. Canting Crew n.p.: Let’s fork him, let us Pick that Man’s Pocket.
1719		A. Smith Lives of Most Notorious Highway-men, etc. (1926) 206: Let’s fork him, i.e., let us pick that man’s pocket, the newest and most dexterous way. This is, to thrust the fingers straight, stiff, open, and very quick into the pocket, and so closing them, hook what can be held between them.
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.
1811		Lex. Balatronicum.
1828		‘The Song of the Young Prig’ in C. Hindley James Catnach (1878) 171: Frisk the cly, and fork the rag, / Draw the fogies plummy.
1830		Lytton Paul Clifford II 99: I have seen the day when there was not a lad in England forked so largely, so comprehensively-like, as I did.
1840		G.W.M. Reynolds (trans.) V. Hugo Last Day of Condemned 38: I fak’d his ticker in my cly, / And fork’d his tin with fingers fly.
1859		‘Ducange Anglicus’ Vulgar Tongue (2nd edn) 45: Three screaves in a lil which I fork’t from a suck Three bank notes in a pocket book which I took from a breast pocket.
1889–90		Barrère & Leland Dict. of Sl., Jargon and Cant.
1935		(con. 1920s) J.T. Farrell Judgement Day in Studs Lonigan (1936) 513: The boy [...] bent over, and forked two bills from the drunk’s pocket.
a.1955		D. Maurer in Lang. Und. (1981) 241/1: fork, v.t. To pick a pocket with the index and middle fingers, using them as pincers.

2. to lay a woman down with spread legs preparatory to intercourse.

1896

Farmer Vocabula Amatoria (1966) 106: Enfourcher. To infemurate or ‘fork’ a woman.

3. (Aus./US, also fork leather) to mount a horse.

1882		J. Aby Hoffenstein 14: Keep off’n that ’ere plug, an’ git somebody as knows how to fork ’em to break him in for you.
1903		A. Adams Log Of A Cowboy 295: So fork that swimming horse of yours and wet your big toe again in the North Platte.
1922		P.A. Rollins Cowboy 65: He still lived on horseback, but regretfully, humiliatingly refrained from [...] ‘forking’ at sight ‘anything on four hoofs’.
1931		‘Stampede’ in T. Goodstone Pulps (1970) 86/1: We gotta fork leather again an’ hunt for three missin’ hombres.
1931		Z. Grey Sunset Pass 6: Ash is as bad a hombre as ever forked a hoss.
1940		O. Strange Sudden Takes the Trail 55: Fork a horse an’ ride hell-bent for the Bar O.
1943		R.L. Bellem ‘Half-Size Homicide’ in Speed Detective Nov. 🌐 You can then re-issue all his old horse operas [...] The public will flock to see them out of pure sympathy, because they know he’ll never fork a cayuse again.
1947		Trail Riders Bul. Feb. 20/2: We forked our cayuses over tuh Rimrock [DA].
1957		D. Niland Call Me When the Cross Turns Over (1958) 140: He’s the greatest roughrider ever forked a horse.
1966		G. & K. Swarthout Whichaway (1967) 61: I forks up my hoss an’ lights out like I was fightin’ bees.

4. to kick in the groin.

1968

A. Burgess Enderby Outside in Complete Enderby (2002) 366: Forked me on the cobbles and no rare-with-Worcester [i.e. mistake].