1892, in C.G. Chaddock's translation of Krafft-Ebing's "Psychopathia Sexualis," from German homosexual, homosexuale (by 1880, in Gustav Jäger), from Greek homos "same" (see homo- (1)) + Latin-based sexual.
'Homosexual' is a barbarously hybrid word, and I claim no responsibility for it. It is, however, convenient, and now widely used. 'Homogenic' has been suggested as a substitute. [H. Havelock Ellis, "Studies in Psychology," 1897]
Sexual inversion (1883, later simply inversion, by 1895) was an earlier clinical term for "homosexuality" in English, said by Ellis to have originated in Italian psychology writing. See also uranian. Unnatural love was used 18c.-19c. for homosexuality as well as pederasty and incest. In 17c.-18c., pathic was used as a noun and adjective in reference to a man that submits to sexual intercourse with another man. Related: Homosexually.
"homosexual person," by 1895, from homosexual (adj.). In technical use, either male or female; but in non-technical use almost always male. Slang shortened form homo attested by 1929.