Entry from OED Online

1637 SHIRLEY Lady of Pleasure v. K1b, Lord. You'le not be angry, Madam. Cel. Nor rude, though gay men have a priviledge. 1700 T. BROWN tr. Fresny's Amusem. Ser. & Com. 130 Every Dunce of a Quack, is call'd a Physician..Every Gay thing, a Chevalier. 1703 ROWE Fair Penit. V. i, Is this that Haughty, Gallant, Gay Lothario? 1754 Adventurer No. 124 7 The old gentleman, whose character I cannot better express than in the fashionable phrase which has been contrived to palliate false principles and dissolute manners, had been a gay man, and was well acquainted with the town. 1791 BURKE Let. to Member Nat. Assembly Wks. VI. 36 The brilliant part of men of wit and pleasure, or gay, young, military sparks. 1798 FERRIAR Illustr. Sterne ii. 40 The dissolute conduct of the gay circles in France is not of modern date. 1847 H. ROGERS Ess. I. v. 214 For some years he lived a cheerful, and even gay, though never a dissipated life, in Paris. 1849 MACAULAY Hist. Eng. vi. II. 103 The place was merely a gay suburb of the capital. 1851 MAYHEW Lond. Labour I. 382 The principal of the firm was what is termed ‘gay’. He was particularly fond of attending public entertainments. He sported a little as well, and delighted in horse-racing. 1891 E. PEACOCK N. Brendon I. 302 This elder Narcissa had led a gay and wild life while beauty lasted. 1897 J. HUTCHINSON Archives Surg. VIII. 224 My patient was a married man, who admitted having been very gay in early life. 1900 G. SWIFT Somerley 54 Oh! that first kiss! how proud of it we are, what gay dogs we feel! 1910 S. KAYE-SMITH Spell Land xix. 221 He felt rather a gay dog.

    b. Hence, in slang use, of a woman: Leading an immoral life, living by prostitution.
 
  1825 C. M. WESTMACOTT Eng. Spy II. 22 Two sistersboth gay. 1857 J. E. RITCHIE Night Side Lond. 40 The gay women, as they are termed, are worse off than American slaves. 1868 Sund. Times 19 July 5/1 As soon as ever a woman has ostensibly lost her reputation, we, with a grim inappositeness, call her ‘gay’. 1885 Hull & Linc. Times 26 Dec. 8/4 She was leading a gay life.
 

    c. Of a person: homosexual. Of a place: frequented by homosexuals. slang.
 
  1935 N. ERSINE Underworld & Prison Slang 39 Geycat,..a homosexual boy. 1951 E. LAMBERT Sleeping-House Party vii. 74 In a way it was an odd threesome. It occurred to me that Esther rather hung round our two gay boys. 1955 P. WILDEBLOOD Against Law I. 23 Most of the officers at the station had been ‘gay’..an American euphemism for homosexual. Ibid. III. 105 The place [sc. a prison] is packed with gay people who are in for something else. 1960 [see BENT ppl. a. 5c]. 1963 A. HERON Towards Quaker View of Sex iii. 24 These may form the ‘queer’ society; these will frequent ‘gay’ bars.
 

 
  absol. 1966 A. FIRTH Tall, Balding, Thirty-Five xv. 194 Would he ever dare, even if he wanted to, join the shrill freemasonry of the London gay? 1968 Globe & Mail Magazine (Toronto) 13 Jan. 6/1 A coffee shop frequented by the gay.
 

    4. slang (orig. U.S.). A homosexual, esp. a male homosexual. Cf. A 2c above.
 
  1971 E. MCGIRR No Better Fiend 69 Until the law was changed..there was a ring of roses around the gays, everybody extorting anything they could get. 1972 Pride of Lions (Columbia Univ.) Apr. 7/3 What about a program acceptable to gays, students and workers? 1974 K. MILLETT Flying (1975) I. 15, I talked at DOB in August, candid, one gay to another. 1975 Whig-Standard (Kingston, Ontario) 13 Aug. 43/5 The female gays in Ottawa are split into four main groups. 1977 Time 25 Apr. 52/3 Florida's former Miss America, Anita Bryant, took time out from her campaign against gays to oppose the ERA. 1980 E. WHITE in Michaels & Ricks State of Lang. 236 Many gays either were in therapy or felt they should be. 1985 Sunday Tel. 30 June 18/7 What about gays, one asks, and will there be facilities for them to relate significantly to each other?