Green’s Dictionary of Slang

1. a confidence trickster, a cheat, esp. when telling ‘sob-stories’ or posing as a deaf-mute.

1781–2		J. Messink Choice of Harlequin I viii: Though you’re a flashy coachman, here the gagger holds the whip.
1786		Whole Art of Thieving 34: Gaggers [...] They are a very deceitful set of people in general, that deserve a prison more than relief: some of them go in a sailor’s dress, pretending that they were galley slaves, and that their tongues were cut out by the Turks, and their arms were burnt in the row gallies: to deceive the world they cut the strings of their tongues, and so swallow it down their throat, that none can perceive it, and make their arms raw by perpetual blisters; but if they were taken to the whipping post, the dumb would speak, and those that walk with crutches would shift without them.
c.1786		Grose Classical Dict. of the Vulgar Tongue ms. additions n.p.: Gaggers. High and Low. Cheats, who by sham pretences, & Wonderful Stories of their sufferings, impose on the Cedulity of well meaning People.
1788, 1796		Grose Classical Dict. of the Vulgar Tongue (3rd edn) .
1811		Lex. Balatronicum [as cit. 1796].
1822		Egan Life and Adventures of Samuel Hayward 50: An hotel [...] distinguished for its life and fun, and visited by all the rum customers upon the pavé, from the four-in-hand whip to the neddy proprietor—traps, gaggers.
1828		Sussex Advertiser 14 Apr. 4/3: [We] soon passed a long string of gaggers, priggers, Adam Tylers, fancy coves, autum [sic] morts, gammoners, sweetners, uprightmen, bully huffs, lully priggers, star gazers, and coves of all sorts.
1835		G. Kent Modern Flash Dict.

2. a broker.

1831

Satirist (London) 4 Dec. 274/1: A meeting of Timber-merchants, cidevant Slave-dealers, Custom-house gaggers, (brokers,) [...] with a sprinkling of dock-wallopers and excise-waiters.

3. a joker; in theatrical context, esp. of comedians, one who ad-libs.

1841		Punch I 69: Men with ‘swallows’ like Thames tunnels, in fact accomplished gaggers and unrivalled ‘wiry watchers’ [F&H].
1887		Era 9 July 15/3: Actors in those days — especially those who played comic parts [...] were incorrigible ‘gaggers’.
1890		Globe (London) 3 Mar. 1/4: The low comedy was much toned down [...] In other words, the gaggers were gagged [F&H].
1900		Era (London) 13 Jan. 9/5: He was a great ‘gagger,’ and gagged through all his speaking parts.
1915		‘Ian Hay’ First Hundred Thousand (1918) 106: The punctilious Mucklewame was still glaring severely after this unseemly ‘gagger’.
1929		Eve. Teleg. (Dundee) 5 Nov. 4/3: [headline] Stage Gaggers who made History. Impromptu Lines in Famous Plays.
1995		(con. 1860s) P. Ackroyd Dan Leno and the Limehouse Golem 78: She might make a good gagger.

4. a tramp, a beggar, who uses ’true’ stories to enhance the basic beggar’s entreaties.

1884		Leicester Chron. 21 June 12/2: ‘Tom the Gagger‘ introduced Fred to a company of seven others.
1910		Derbys. Advertiser 2 Dec. 25/4: ‘Gaggers,’ the higher class of treamps, with their plausible tales.
1912		Leamington Spa Courier 20 Sept. 7/1: There are a great many tramps staying in this district at the present time [...] We have among us ‘gaggers’ (beggars).
1933		‘George Orwell’ Down and Out in Complete Works I (1986) 176: These (omitting the ones that everyone knows) are some of the cant words now used in London: [...] A gagger – beggar or street performer of any kind.

5. (US Und.) a receiver of stolen goods.

1949

Monteleone Criminal Sl. (rev. edn).

6. (US tramp) a tramp who makes a living by telling stories.

1956

F.O. Beck Hobohemia 47: Some of his associates are ‘gaggers’ who get their living — a scanty one — by telling tales.