Green’s Dictionary of Slang

1. (also yap it up) to talk, to make a noise, esp. to shout at, like a dog; thus yapper, n. a gossip; yapping n. and adj.

1823		‘Jon Bee’ Dict. of the Turf, the Ring, the Chase, etc. 196: A man with a snarling manner, or replete testy replies — yappeth.
1841		J. Mills Old Eng. Gentleman (1847) 253: What are ye all yapping for? I am not deaf.
1866		‘George Eliot’ Felix Holt II I 143: Moro yapped in a puppy voice at their heels.
1891		G.R. Sims ‘The New Cure’ Dagonet Ditties 101: My fingers I can snap / At the Opposition folly, / And the Parnellites who yap.
1899		J. Flynt Tramping with Tramps 384: ‘I’m starvin’, father,’ I yapped.
1905		Sun. Times (Perth) 26 Nov. 4/7: To stand up there in Parliament / And yap / And yap / And yap.
1914		N.Z. Observer 6 June 4/1: He asked no e‘what are you yapping at?’.
1915		C.J. Dennis ‘The Intro’ in Songs of a Sentimental Bloke 23: I’m yappin’ to me cobber uv me mash . . . / I’ve done me dash!
1915		Sport (Adelaide) 15 Jan. 5/1: One or two of the yappers have been keeping fairly quiet lately.
1917		Union Jack 5 May 17: Well, what of it you yapping coward?
1920		S. Lewis Main Street (1921) 420: Next thing, I suppose you’ll be yapping about free speech. Free speech!
1925		Wodehouse Carry on, Jeeves 79: I’ve hurried along Piccadilly and felt the hot breath of the toucher on the back of my neck and heard his sharp, excited yapping.
1930		G. Milburn ‘Hash’ in Hobo’s Hornbook 212: We braced a gent on the downtown side, / And told him our story straight, / He didn’t yap for a dick, but grinned.
1946		Mezzrow & Wolfe Really the Blues 157: I kept yapping at them every time they drifted off [...] from the pure style.
1957		‘Nino Culotta’ They’re a Weird Mob (1958) 13: How difficult it is for the foreigner, who has learned good English from books, to understand what the blazes they are yapping about!
1964		H. Selby Jr Last Exit to Brooklyn 88: Of course the kid started yappin but they took care of it.
1976		P. Theroux Family Arsenal 202: I thought she had more sense than to go yapping about her sordid past.
1988		B. Humphries Complete Barry McKenzie 11: Reckon I’m yappin’ to meself again.
1991		B. Hamper Rivethead (1992) 141: The sounds of my co-workers yapping it up and tossing ’em down.
1999		Guardian Saturday Rev. 12 June 9: She can also yap away merrily about primitive condoms.
2000		Indep. Rev. 28 Jan. 7: A cross-looking girl with a finger in one ear is yapping: ‘Well tell Sebastian to get his arse over here right now.’.
2011		F. Bill ‘Trespassing betwen Heaven and Hell’ in Crimes in Southern Indiana [ebook] ‘I’d have maybe thought before I started yappin’ my jaws’.
2020		D. Winslow ‘Crime 101’ in Broken 77: [M]ost crimes are solved because someone yaps.

2. (US) to complain, to nag.

1900		C.J.C. Hyne Filibusters 6: Only a few newspapers who do not understand, or who are interested in the other party, will yap.
1908		Bulletin (Sydney) 12 Nov. 40/2: Then th’ bloke what owned th’ saloon starts yappin’. ‘Yer ruinin’ me place,’ he says. ‘Shut yer head about yer place,’ we says.
1937		W.M. Raine Cool Customer 126: Then everyone yaps at us because we don’t run down the criminals.
1955		‘Hal Ellson’ Rock 4: ‘I’m not chicken.’ ‘I’d like to see it.’ ‘Then don’t yap. Come along.’.
1965		C. Himes Cotton Comes to Harlem (1967) 19: Nerwspapers have been yapping about police brutality.
1974		G.V. Higgins Cogan’s Trade (1975) 23: I’m yapping at the kids all the time [...] giving them hell.
1997		H.R.F. Keating Soft Detective 244: You shouldn’t do that, Belinda. On and on, yap-yap-yap.
1997		Share Slanguage.

3. (Aus.) to tell, to recount.

1909

‘A “Push” Story’ in Bulletin (Sydney) 2 Sept. 17/1: ‘’N’ what drove th’ demons t’ muck up th’ college?’ ‘Well, it takes some constant chat, Squezzer ; but I’m fit t’ yap it, all in. Th’ school wuz in ’n’ goin’ gay’.