This word is derived from the proper adjective Lesbian = 'belonging to the island of Lesbos' and has acquired its present day sense by association with the poet Sappho. The word lesbian was formerly applied to homosexual women as a cover word or euphemism, but it is now widely accepted as the term preferred by homosexual women themselves:

"All of us millions of lesbians and gay men were once American children." - Jean O'Leary and Bruce Voeller, New York Times

The original sense ('from Lesbos') has fallen out of use.