Crotch has the etymological history Probably a variant of 'crutch' (Old English 'cryċċ', 'staff with a forked support'), influenced by 'crotchet'; the sense is 'the forking place'. The immediate etymological form is Old English cryċċ. In present use as a noun, it means "the angle where the legs or two branches fork apart", keeping the historical formation close to the word's ordinary semantic work. Related words include crutch and crook; derived forms include crotched. The surrounding word family keeps the same base visible in crotched, crutch, and crook, showing how the headword belongs to a larger cluster rather than standing alone.