Green’s Dictionary of Slang

1. to betray, to inform against.

c.1590		Jeronimo (1605) Diii: Nay Lord Lorenzo, whers the pardon? Sfoot Ile peach else.
1607		Dekker & Webster Northward Hoe V i: I haue known an arrant thief for peaching made an officer.
c.1616		Fletcher Bloody Brother III ii: You, chip, Pantler, you peaching rogue.
1654		New Brawle 12: Out, ye Whidling Shammock you, if you had not peach’d Sirrah, ye might have both been nubb’d like two Roagues together, but the Hemp was not ripe.
1663		S. Butler Hudibras Pt I canto 1 line 599: Make Mercury confesse and peach / Those thieves which he himself did teach.
1697		M. Pix Innocent Mistress V iii: Ay, my own mother to save myself. I say we’ll peach.
1712		J. Arbuthnot Hist. of John Bull 88: Yan Ptschirnsooker came off (as rogues usually do upon such occasions) by peaching his partner.
1727		J. Gay Beggar’s Opera I x: Secure what he hath got, have him peache’d the next Sessions, and then at once you are made a rich Widow.
1731		Fielding Letter Writers II xi: mr. wisd.: It were good for you to resolve on being an Evidence, and save your own Neck at the Expence of his. risq.: Well, Sir, if I must peach, I must, I think.
1766		Colman & Garrick Clandestine Marriage V ii: I’d sooner die than peach.
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.
1797		M. Leeson Memoirs (1995) III 194: I was apprehensive in revenge he would ‘peach’.
1811		Lex. Balatronicum.
1818		‘Thomas Brown’ Fudge Family in Paris letter VI 56: Give me the useful peaching Rat.
1827		P. Cunningham New South Wales II 254: Honest John [...] was induced to ’peach on account of Jones (whom he denounced as being in reality the greatest ruffian in all Wales).
1838		Dickens Oliver Twist (1966) 107: Clever dogs! Staunch to the last! Never told the old parson where they were. Never peached upon old Fagin!
1845		Nat. Police Gaz. (NY) 11 Oct. 57/4: ‘You’d “peach” and turn “black spy”’.
1848		G.W.M. Reynolds Mysteries of London II (2nd series) 261: He might be induced to peach against Bob.
1851		‘Greenhorn’ [G. Thompson] Bristol Bill 13/1: [H]e paced the room muttering to himself, expressions with regard to ‘peaching,’ and ‘the gang’.
1855		T. Taylor Still Waters Run Deep II ii: Surely that wildcat of a woman knows better than to carry out her threat of peaching.
1857		Mt Alexander Mail (Vic.) 24 Apr. 3/3: [P]ersons who band themselves together for a criminal purpose cannot be depended upon, and [...] they will, to use their own slang, ‘peach upon their pals’.
1861		T. Hughes Tom Brown at Oxford (1880) 126: I’m not going to peach if the proctor don’t send again in the morning.
1874		J. Greenwood Wilds of London (1881) 169: A curse on the sneak who shall peach, or shall shake.
1881-2		T.B. Reed Fifth Form at St Dominic’s (1890) 32: ‘Wretched little sneak! [...] I suppose he’ll go peaching to his big brother’.
1885		Ledger (Noblesville, IN) 14 Aug. 6/2: ‘His partner “shaded” him and then “peached”’.
1888		‘Rolf Boldrewood’ Robbery Under Arms (1922) 98: Not much chance of his peaching, if it had been a hanging matter.
1890		Bulletin (Sydney) 23 Aug. 24/2: It is possible [...] that the increment of £2 6s. 8d. to his salary, which he would receive monthly, could he supplant Mitchell, would be useful in his wedded state, had something to do with his ‘peaching’ on the Overseer.
1897		E.W. Townsend Chimmie Fadden 53: I was dead sore cause she was peaching on me.
1899		‘Pot’ & ‘Swears’ Scarlet City 75: I’ve just been and told Mrs Wagstaff everything. She, dear lady, won’t peach.
1901		J. Flynt World of Graft 130: Peach on your companions, be just as mean and traitorous as you know how to be in our interests, and we will give you a certain amount of protection.
1906		E. Pugh Spoilers 279: ‘You ain’t a proper man at all,’ she said with slow contempt. ‘If you was [...] you wouldn’t go an’ peach, like a stinkin’ nark!’.
1911		S. Ford Torchy 169: You wouldn’t be cad enough to peach on us for smokin’, would you?
1916		Joyce Portrait of the Artist as a Young Man 4: His father had told him [...] whatever he did, never to peach on a fellow.
1922		F.S. Fitzgerald ‘The Diamond as Big as the Ritz’ in Bodley Head Scott Fitzgerald (1963) V 63: How about trusting us not to peach on you?
1926		N. Lucas London and its Criminals 145: She ‘peached’ on a woman [...] The woman swore vengeance and when she came out a month or two ago she attacked Peggy with vitriol.
1930		(con. 1910–20s) D. Mackenzie Hell’s Kitchen 168: Whether he was ‘lolly popped’ (peached upon) or whether he was ‘shopped’ (given away by confederates) I am not sure.
1930		Eve. Herald (Dublin) 9 Dec. 4/6: Other [underworld] terms include : — ‘Flatty’ (policeman), ‘peach’ (to give away), ‘Peter’ (safe), ‘monkey’ (padlock), ‘stick’ (jemmy), ‘van dragger’ (motor thief), ‘snow’ (cocaine), ‘madam’ (misleading conversation) ‘stir’ (prison).
1949		Monteleone Criminal Sl. (rev. edn).
1950		Goldin et al. DAUL 154/1: Peach. (Obsolescent) To inform; to confess guilt and implicate associates.
1980		‘John le Carré’ Smiley’s People 238: Karla is either smelling a rat or Mikhel has peached.
1989		J. Morton Lowspeak.

2. to confess, to admit.

1866		J. Greenwood Little Ragamuffin 106: He’s done something more’n he peaches to, only he won’t say.
1944		E. Wilson 27 June [synd. col.] So,me foul, horrid tattle tale has peached to him that they may be wanting him [...] to accept the Republican n----a---n.
1950		see sense 1.