Word Origin & History
fanny"buttocks," 1920, Amer.Eng., from earlier British meaning "vulva" (1879), perhaps from the name of John Cleland's heroine in the scandalous novel "Fanny Hill or Memoirs of a Woman of Pleasure" (1748). The fem. proper name is a dim. of Frances. The genital sense is still the primary one outside U.S.,
but is not current in Amer.Eng., which can have consequences when U.S. TV programs and movies air in Britain.