Green’s Dictionary of Slang

(orig. US) to stop talking; esp. in imper.

1939		Howsley Argot: Dict. of Und. Sl. 53: use the zipper – keep the mouth shut, reveal nothing.
1942		R.L. Bellem ‘Malibu Mess’ Dan Turner – Hollywood Detective Dec. 🌐 Both of you keep your yaps zippered about what’s happened.
1943		R.L. Bellem ‘Half-Size Homicide’ in Speed Detective Nov. 🌐 My best bet was to zipper my kisser until I had a chance to snoop around.
1949		R. Service ‘Montreal Maree’ in Songs of a Sun Lover (1955) 73: Now though I zippered up my mug somehow the story spread / That I was playin’ poker and my banker was Maree.
1958		(con. WWII) F.I. Gwaltney Heaven and Hell 52: I made a gesture of zipping up my mouth and Wille passed back a no-talking order.
1959		W. Brown Teen-Age Mafia 9: They played it cool [...] kept their lips zipped.
1962		P. Crump Burn, Killer, Burn! 13: Dammit, Dipper, zip your lip.
1966		M. Rumaker Exit 3 and Other Stories 66: Sam, you zipper your trap. [...] Let Carp go on and tell the story.
1971		F. Hilaire Thanatos 133: Nobody told me to keep my lip zipped.
1979		T. Alibrandi Custody 283: I want you, mentally, to turn off your hearing aid and zip up your mouth.
1982		A. Maupin Further Tales of the City (1984) 199: ‘I want this to be . . . official, Father.’ ‘Meaning, zip the old lip, huh?’.
1985		T.R. Houser Central Sl. 46: Don’t be puttin no salt in my game, zip your fat mouth and let me finish.
1991		P. Cornwell Body of Evidence (1992) 211: Sometimes he snitches a little, other times he zips his lip.
2001		(con. 1964–8) J. Ellroy Cold Six Thousand 641: She said no more. She zipped her lips and played coy.
2004		T. Dorsey Cadillac Beach 189: You a news-fink? My trap’s zipped.
2011		J.J. Connolly Viva La Madness 369: Ted nods, lips zipped.
2015		L. McInerney Glorious Heresies 91: ‘It’d be more in your line to try zipping your trap’.
2020		C. Hiaasen Squeeze Me 249: ‘[H]ow much you want in order to keep your big mouth zipped?’.