"A muscle of the foot corresponding to the opponens pollicis of the hand, best developed in certain apes and monkeys and seldom distinguished as a separate muscle in humans", Late 19th cent.; earliest use found in Science. From scientific Latin opponens hallucis from classical Latin oppōnēns + scientific Latin hallucis, genitive singular of hallux great toe.[opponens hallucis etymology, opponens hallucis origin, 英语词源]