gay [ME] In its original sense of ‘light-hearted and carefree, exuberantly cheerful’, gay goes back to the 12th century and derives from Old French gai. By the 17th century the meaning had extended to ‘addicted to social pleasures’, often with an implication of loose morality, as in, for example, the expression gay dog [M19th] (a man fond of revelry), or these lines from William Cowper’s poem ‘To a Young Lady’ (1782): ‘Silent and chaste she steals along / Far from the world’s gay busy throng’. In slang use the word could describe a prostitute. The use of gay to mean ‘homosexual’, now the main meaning, is unambiguously found in examples from the 1920s, though there is evidence that it may have been used in this sense earlier.