Crotch
mid 16th century (denoting an agricultural or garden fork, also a crutch): perhaps related to Old French croche ‘crozier, shepherd's crook’, based on Old Norse krókr ‘hook’; partly also a variant of crutch.
wiktionary
Of disputed origin; two possibilities seem likely:
etymonline
crotch (n.)
1530s, "pitchfork," from Old North French croche "shepherd's crook," variant of croc "hook," from Old Norse krokr "hook," which is of obscure origin but perhaps related to the widespread group of Germanic kr- words meaning "bent, hooked."
From 1570s as "any fork or forking," especially "a parting of branches of a tree;" meaning "region where the body forks" is attested from 1590s. Hence crotchcutter "women's bathing suit with leg openings which reach above the hips" (by 1997).
