Green’s Dictionary of Slang

to talk excessively.

1924		Star Phoenix (Sakatoon, Saskatchewan) 9 Apr. 1/4: Their journalistic sympathizers, gas-bagging about the physical difficulties of the route.
1943		San Bernardino Co. Sun (CA) 31 Jan. 2/4: It must be the greatest shame for a German if he, instead of working or fighting, is gas-bagging and criticizing.
1959		I. & P. Opie Lore and Lang. of Schoolchildren (1977) 214: Stop gasbagging.
1966		Windsor Star (Ontario) 18 Apr. 21/1: Delay [...] gas-bagging and red tape.
1986		Times-News (Twin Falls, IA) 11 Oct. 6/2: Anyone who preaches that Jesus is ‘King of the Jews’...is a ‘lying gas-bagging preacher’.
1998		Age (Melbourne) 12 Apr. 120/2: ‘You’ve been gas-bagging all afternoon’.
2000		W.F. Laurance Stinging Trees and Wait-A-Whiles 60: Sometimes we’d gasbag for a half hour or more.
2007		L. Redhead Cherry Pie [ebook] ‘Enough of this gasbagging. You’ve got to hit the road’.
2017		Lincon Jrnl Star (NE) 25 Feb. D5/5: Gasbagging on about themselves, [...] demonsrating a lack of interest in others.
2023		(con. 1962) J. Ellroy Enchanters 387: Albie gasbagged on the Leopold-Loeb case.