Gay is a complicated little word. On the one hand it refers to male or female homosexuals (e.g., "The gays all live in San Francisco." or "She just told me she's gay."). But it's also used to describe something or someone considered weak, lame or inferior (e.g., "That's so gay." or "Stop being so gay.").
Coincidence? Probably not. This second use of the word likely grew out of the first--people who are homosexual (especially men) have historically been accused of being weak and inferior. For this reason, many people find this use of the word offensive.
Of course, "gay" originally meant merry or happy--it's from the Old French word gai. But it's had a sexual meaning for over a hundred years. In the 19th century, prostitutes in England were said to dress "gaily." In that historical context, gay meant merry, or joyous, as the prostitutes dressed in a cheery fashion. Brothels were called "gay houses."
The word took on its homosexual connotation in the early 20th century in the United States. Within the hobo community homeless boys would look to an older man on the street, or a "gay cat," for survival skills. The relationship between the two companions was sometimes sexual, so the word "gay" took on its current meaning. By the 1920's homosexuals began using the word to describe each other. The earliest uncontested use of the word is in Noel Coward's 1929 musical "Bitter Sweet."
Today the word "gay" is widely used--both within the gay community and without--as a neutral way to describe someone who is sexually attracted to members of the same sex.
