English
horseproof
From horse + -proof.
Formed from horse + -proof
Proto-Germanic *hrussą ‘horse’
Proto-West Germanic *hross ‘horse’
Old English hors ‘horse’
Middle English hors ‘a horse’
English horse
Today it means
adj Resistant to horses; preventing a horse from escaping.
Language periods are conventional ranges, not dates for this word.
Etymograph / horseproof