opponent (n.)youdaoicibaDictYouDict[opponent 词源字典]
1580s, from Latin opponentem (nominative opponens), present participle of opponere "oppose, object to," literally "set against, set opposite," from ob "against" (see ob-) + ponere "to put, set, place" (see position (n.)).[opponent etymology, opponent origin, 英语词源]