Green’s Dictionary of Slang

1. puffy, swollen, esp. of the ankles of a horse or human.

1772		Bridges Burlesque Homer (3rd edn) 497: The Trojans do so sorely pelt, / That if his potlid and his belt / Did not secure his rump so gummy, / His buttocks must be thrash’d to mummy.
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue n.p.: Gummey, clumsey, particularly applied to the ancles of men, or women, and the legs of horses.
1802		G. Colman Yngr Poor Gentleman IV i: luc.: Bless me! I can never get over that stile! olla.: A little gummy in the leg, I suppose.
1811		Lex. Balatronicum.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.
1838		R.S. Surtees Jorrocks Jaunts (1874) 133: What gummy legs that girl in green has!
1860		Hotten Dict. of Modern Sl. etc. (2nd edn) 151: GUMMY, thick, fat — generally applied to a woman’s ancles [sic].
1866		Letters by an Odd Boy 162: Why should I call an individual obese of ’person and weak of intellect ‘-a gummy gulpin ?
1870		Hotten Sl. Dict. [as cit. 1860].

2. (also gummy) clumsy, drunken.

1842		Nichols’ Wkly Arena (NY) 4 June n.p.: She was earnestly solicited to remain all night, by some of the gummed inmates.
1860		Hotten Dict. of Modern Sl. etc. (2nd edn) 151: GUMMY, thick, fat — [...] a man whose flabby person betokens him a drunkard.
1870		Hotten Sl. Dict. [as cit. 1860].

3. (US drugs) used of one who has become lethargic after smoking cannabis.

1952		(con. 1948) G. Mandel Flee the Angry Strangers 76: She was glad she’d told him [...] glad in the gummy calm Lukey’s smoke had lent her. [Ibid.] 171: Gummy darkness rolled inside her.
2003		Dictionary at Smokeforpeace.com 🌐 Gummy – To become lethargic after smoking.