Green’s Dictionary of Slang

dyke n.

also dike
[ety. unknown; ? f. dyked down, dressed up; certainly some lesbians have always dressed as men. Another theory suggests the gradual corruption of SE hermaphrodite to morphodite to dike and dyke and thence, with the masc. generic bull, to bull-dyke n. and bull-dagger under bull n.1 ; however, the first use of bull-dyke n. appears to predate dyke, which may thus be an abbr.]

[1930s+] a lesbian.

In compounds

dykeface (n.)

[1990s+] a general term of abuse, aimed at a woman; lit. ‘lesbian-face’.

dyke-hag (n.) [on pattern of fag-hag n.2 (1)]

[2000s] (S.Afr. gay) a man, usu. heterosexual, whose friends are lesbians.