Gay historians say that the term came into popular use in the 1950's as gays and lesbians developed a special connection with Judy Garland, whose ballads of hope and despair and whose relentless spirit, and tragic history, mirrored their struggles in everyday life. She wasn't the first diva or drama queen, but certainly the one who resonated the most to a generation of gays and lesbians. Garland's most famous role -- as the ever-optimistic and wistful Dorothy in the 1939 classic "The Wizard of Oz" -- gave gays and lesbians a "secret" code word which they could use to refer to themselves. At cocktail parties or company gatherings where one could not be comfortably "out and proud," gays would inquire discreetly of each other, "Are you a 'Friend of Dorothy?'" The wink-wink admission of "I am, too!" would likely lead to fabulous and fast bonding in an age when gay bars were clandestine, and in some cases dangerous.
Today, the term is used mostly by Baby Boomers and an older generation of gays and lesbians; the gay members of MTV kids and Generations X and Y would probably not recognize the meaning of "FOD" unless they learned it from some older friends!