Green’s Dictionary of Slang

1. a male homosexual, thus constr. with the, homoxexual men seen as a group; thus gayety n., a state of homosexuality.

c.1925		R. McAlmon Lodging House (1963) 94: After all he argued to himself, he was sure Miss Gay was not interested in women and Steve [female] would surely start trying to get off with her as soon as she had one cocktail.
1949		‘Swasant Nerf’ Gay Girl’s Guide 36: How to Distinguish Readily Between the Gay and Various Kinds of Trade.
1951		‘D.W. Cory’ Homosexual in Amer. 98: [M]any of the gay graduate with the highest honors.
1957		J.M. Reinhardt Sexual Perversion 42: The average here differed from that of the ‘gays’ however [Simes:DLSS].
1963		J. Rechy City of Night 33: The queens swished by in superficial gayety.
1966		T. Erikson Half World Amer. Homosexual 24: The street shines through the night, and this independent world of the gay congregates till dawn [Simes:DLSS].
1969		Wash. Post and Times Herald 25 Oct. C2/1: The reaction gap between gays and straights to these plays is further.
1973		M. Scorsese Mean Streets [film script] 18: There are only a few customers left in the club, including Michael and two gays.
1985		‘Thommo’ Dict. Aus. Swearing & Sex Sayings 56: GAY — Male or female homosexual, a word used by homosexuals to describe themselves.
1989		T. Blacker Fixx 133: A well-known film star (and undeclared gay).
1998		‘P. Parivaraj’ Shiva & Arun 124: He [sc. a Muslim] often thought that his problem must be like a Brahmin gay telling his father that the Kama Sutra and the wall engravings at Puri temple were real [Simes:DLSS].
1999		N. Cohn Yes We have No 201: The clientele there is mixed – small-time crims, old gays, bikers.
2000		Observer 9 Jan. 5: Commanding officers will not be expected to tolerate gays mincing across the parade ground.
2005		H. Mantel Beyond Black 220: This is Surrey. They don’t get many gays.
2011		IOL News (Western Cape) 4 May 🌐 What kind of father would give away his lovely, educated daughter to a gay?

2. (Aus. Und., also gaylo) a gullible victim, i.e. of a swindler, a ‘civilian’ [no overt sense of homosexuality but a poss. link is hard to ignore].

1932		New Call (Perth, WA) 21 Apr. 12/7: [A] young woman [...] informed the company that she had just ‘touched off’ a ‘gay’ which I learned meant that she had picked a man’s pocket.
1936		Queenslander (Brisbane) 2 July 4/4: So, out to crop the wisdom I did sow, And with much daring took a ‘gay’ in tow. / But this was all the harvest that I reaped, / I touch the ‘mug’ - he squeals - and in I go!
1938		Smith’s Wkly 21 May 6/4: I remember meeting [...] ‘Tibby,’ greatest of all Australian ‘whizzmen’ (pickpockets). [...] ‘Blime,’ he roared, ‘I been working with a gay (mug), and taking risks in the ‘rort’ (crowd) for a ‘bloodhoon’ who never lifted a ‘leather’ (wallet) in his life’.
1945		S. Baker Aus. Lang. 142: I append a vocabulary supplied to me by an ex-con man. […] Here is his glossary with the Australianisms italicized and some notes on the non-Australian elements: alec, dill, gay, sim, lolly, bunny, and mug.
1945		Smith’s Wkly (Sydney) 8 Dec. 22/3: ‘Once,’ said the punter, ‘I was gloomy and glum, / A gig and a gaylo, a nitwit and dumb. / From my ears to the top of my head I was numb’.
1949		Cessnock Eagle (NSW) 4 Oct. 4/2: They took a picture to identify me. / Then forty demons said ‘just nod your head and you’ll be free’ / So I pleaded ‘Guilty’ just like a ‘gay’ / Now I’m a boarder out at Long Bay.
1954		Truth (Brisbane) 5 Dec. 26/6: ‘What, leave Aussie and go and live in the Old Dart, [...] Strike me lucky, you must think a man’s a real gay!’.
1977		J. Ramsay Cop It Sweet 39: GAY: Trickster's victim; Not very smart person.

3. (mainly UK juv.) a term of abuse for an unpopular individual.

1947		Aus. Worker (Sydney) 20 Aug. 12/4: O’Connor has never been able to really satisfy himself as to an appropriate name for the class of man who is prepared to bludge on his workmates [...] he has been known to describe these parasites as ‘toads,’ ‘woolly-noses,’ ‘twirps,’ ‘dillpots,’ ‘nit-wits,’ ‘gays’ and ‘scabs’.
1999		Indep. Education 8 July 2: ‘Gay’ and ‘lezzie’ [...] are generalized terms of abuse, used against youngsters, particularly boys, who deviate from the norm.

4. (US gay) a lesbian.

1993

(con. 1940s-50s) Kennedy & Davies Boots of Leather (2014) 7: For both [hetero- and homosexual] communities the term ‘gay’ was more prevalent in the 1950s than in the 1940s.