Green’s Dictionary of Slang

1. (US campus) a lesson one has not learned properly; a lesson learned by any form of cheating aid.

1856		B.H. Hall College Words (rev. edn) 431: A lesson learned by hearing it read by another; borrowed ideas; anything plagiarized.
1900		E.H. Babbitt ‘College Words and Phrases’ in DN II:i 60: skin, n. A paper, book, or other means unlawfully used in an examination.

2. (UK und.) a robbery.

1858

‘Shadow’ Midnight Scenes 111: The cellar below [...] dark as the grave, and celebrated, we are informed in professional language, for ‘many a good skin,’ or robbery.

3. a cheat; a liar.

1882		Nat. Police Gaz. (NY) 3 June 3/2: He Is about the only manager of the lot who isn’t in some respect or other a professional ‘skin’ given to half salary tricks and dodging hotel bills.
1883		Nat. Police Gaz. (NY) 15 Dec. 14/4: The wrestling tournament at Ansonia was gotten up by a couple of dead skins [...] who had things cut and dried for their heavyweight [...] to win.
1900		E.H. Babbitt ‘College Words and Phrases’ in DN II:i 60: skin, n. One who cheats or deceives.
1926		Wood & Goddard Dict. Amer. Sl.

4. that which deceives or cheats.

1897

A.H. Lewis Wolfville 15: I now announces that this yere game is a skin an’ a brace.

5. (US) a crooked gambling establishment.

1903

Inter Ocean (Chicago) 25 Jan. 34/5: I [...] went down to John L’s to see if the old man could put me wise to the bogus banks [...] ‘Say, young feller [...] There are more skins on that block than there are in a tanyard’.