Green’s Dictionary of Slang

gasbag n.

also gasman
[gas n.1 (1)]

a talkative person.

[US]Ladies’ Repository (N.Y.) Oct. VIII:37 316/2: Gasman, a braggart.
[US]Life in Boston & N.Y. (Boston, MA) 23 Aug. n.p.: You and those three gas bags had better keep away.
[US]J.W. Haley Rebel Yell and The Yankee Hurrah (1985) 250: He was a cheap buffoon and the very prince of gasbags.
Newton Kansan 2 Jan. 2/3: Gas bags were never known to do more than make a noise [DA].
[UK]Manchester Eve. News 4 Feb. 4/4: ‘Fiddlesticks,’ cried Knowall. ‘Do you suppose I would be fool enough to employ a — a gas bag like you?’.
W. Kansas World (Wakeeny, KS) 3 Oct. 1/4: ‘Capt.’ Glaspie is the worst old blister west of the Alleghanies. His talk is foul and indecent. He is commonly known as the Pawnee ‘gasbag’.
[UK]Referee 6 Jan. n.p.: That great gas-bag of modern days [F&H].
[Aus]Truth (Sydney) 17 Mar. 6/4: Had Patrick got John L. into the ring, the Maitlander would have been champion instead of the gas-bag that now poses as boss of the world.
[UK]Binstead & Wells Pink ’Un and Pelican 186: That vain old gasbag, Sir William Vernon Harcourt.
[Aus]‘Dads Wayback’ in Sun. Times (Sydney) 8 Mar. 5/3: ‘True A1 bounders is gas-bags; theys got ter be bulgy an’ full o’ wind ter make ’em bounce. [...] an’ he can go on spoutin’ jest as long as ther gas is laid on’.
[US]‘O. Henry’ ‘The Clarion Call’ Voice of the City (1915) 195: Kind of rattles you, doesn’t it, to have the mysterious villain call up [...] and tell you what a helpless old gas-bag you are?
[US]J.C. Lincoln Shavings 16: I judge likely I’m the ‘this’ you and that gas bag have been talkin’ about.
[UK]E. Raymond Tell England (1965) 83: Kick that gas-bag Pennybet out.
[Aus]Townsville Daily Bull. (Qld) 10 Aug. 16/2: One old gasbag said there was no disease or trouble.
[UK]E. Raymond Child of Norman’s End (1967) 362: A trifler, and a gas-bag to boot.
[US]O. Strange Sudden Takes the Trail 62: You ain’t scared o’ that gas-bag, are you?
[US]S. Lewis World So Wide 163: I’m going to collect as many facts [...] as that old gas-bag, Belfont, has in maybe twenty years.
[UK]I. & P. Opie Lore and Lang. of Schoolchildren (1977) 68: One who talks too much (i.e. a chatter-box, gas-bag, [...] or wind-bag).
[US]K. Kolb Getting Straight 77: Poor old gasbag.
[UK]D. Nobbs Fall and Rise of Reginald Perrin (1976) 142: What have you two gas bags been talking about?
[US]H. Rawson Dict. of Invective (1991) 170: The person who talks too much is, naturally, a gasbag.
[Aus]G. Seal Lingo 2: Although mostly taken for granted, the importance of the vernacular in everyday life is apparent from the number of Lingoisms describing or referring to it. chinwag; gasbag; have a yarn; bend your ear.
[US]Baltimore Sun (MD) 4 Jan. D5/1: He always seems to have something worthwhile to say. There is not an ounce of gasbag in him.

In derivatives

gasbaggery (n.) (also gasbag)

(Irish) empty wordiness, prolixity.

[Ire]Wexford People 17 Feb. 4/4: [J]ust let the Government exhibit any disposition to keep the peace, and all the loyal and disloyal gas-baggery will collapse.
[UK]Sporting Life 19 Aug. 2/4: R. Goodman is the Leadinq Turf Telegraphist and the man to follow. [...] No guesswork. No Twaddle. No Continental nor Chinese Napoleonism. No incompetent gas-baggery. No clap-trap.
[US]Morn. Post (Raleigh, NC) 24 July 9/2: Politics, oratory, debate, contention, humbuggery, and gasbaggery.
[Can]Saskatoon Dly Star (Saskatchewan) 29 July 4/3: Condor Charlie [i.e. Lord Charles Beresford] already has sufficient of a reputation for gas-baggery.
Dly News (London) 17 Mar. 10/3: [T]he incessant wrangling, disputation and gas-baggery of the House of Commons.
Brookyln Dly Eagle (NY) 4 Nov. 34/3: [P]olitical mugwumpery and gasbaggery.
[US]Danville News (TX) 27 Feb. 1/1: Politicians had developed the fine art of gasbaggery to its supreme height.
[US]R. Baker 26 Apr. [synd. col.] ‘Radicalization’ may also mean [...] a new tendency to indulge in political gasbaggery.
[US]E. Torres After Hours 184: Mickey Mouse intellectual. Still showin’ off, he got off on Dave and the two of them went into a heavy literature gas-bag.
Age (Sydney) 23 June 11/1: [T]he talk of politicians was accurately described as ‘hot air,’ ‘gas-baggery’, ‘political wind’ [etc].
[Ire]Sun. Tribune 17 May B13: He hated cant and gasbaggery, and went unerringly to the centre of things.
Dly Telegraph (London) 30 June 26/2: Clinton outdoes all rival practitioners of the higher gasbaggery.
[Ire]L. McInerney Glorious Heresies 298: She lost interest in her detective novels [...] she didn’t have the time for cheesy gasbaggery.
[Can]Regina Leader-Post N12/1: [G]asbaggery about how Auston Matthews tapes his hocley stick.
Tallahassee Democrat (FL) 28 Apr. A5/4: Facts belie the gasbaggery. Math produces facts.