English
horsefucker
From horse + fucker.
Proto-Germanic *hrussą ‘horse’
Proto-West Germanic *hross ‘horse’
Old English hors ‘horse’
Middle English hors ‘a horse’
English horse
The story
Sense 2 was derived from the fans' show involving cartoon horses, or the adult-oriented fans of the show making erotic artwork of the characters.
Today it means
noun A term of abuse.
Language periods are conventional ranges, not dates for this word.
Etymograph / horsefucker