The expressions third gender and third sex date as far back as the 17th century, at the time connected with an emerging subculture of effeminate males and a marked increase in hostility towards effeminate or homosexual men. The terms continued to exist as popular descriptors of homosexuality and cross-gender into the 20th century, but fell out of favour with gay liberation in the 1970s and a growing recognition of sexual orientation and gender identity as separate concepts. Their renewed use in more recent times is partly attributable to a greater understanding of biological sexual variation and a realization that the human body cannot always be neatly categorized as one of two sexes.

The expressions third gender and third sex date as far back as the 17th century, at the time connected with an emerging subculture of effeminate males and a marked increase in hostility towards effeminate or homosexual men. The terms continued to exist as popular descriptors of homosexuality and cross-gender into the 20th century, but fell out of favour with gay liberation in the 1970s and a growing recognition of sexual orientation and gender identity as separate concepts. Their renewed use in more recent times is partly attributable to a greater understanding of biological sexual variation and a realization that the human body cannot always be neatly categorized as one of two sexes.