Green’s Dictionary of Slang

1. (US) one who engages in bisexual oral sex.

1964		‘R. Blake’ Amer. Dict. Sexual Terms 17: bi-lingual (Vulg Sl) adj. Referring to a person who will perform oral intercourse on both sexes; a bi-sexual who prefers oral-intercourse. n.
1972		R.A. Wilson Playboy’s Book of Forbidden Words.

2. (orig. US gay) referring to one who licks and sucks both the anus and penis of his partner.

1988

H. Max Gay (S)language.