Meaning

adjective consisting of or having the hardness of adamant

adjective having the hardness of a diamond

adjective impervious to pleas, persuasion, requests, reason; ; - W.Churchill

originFrom Middle English adamantine, adamantyne, adamauntyn (“(adjective) of adamant; (noun) adamant”), from Anglo-Norman adamantin and Middle French adamantin (“of or resembling adamant or diamond”) (modern French adamantin), and from its etymon Latin adamantinus (“adamantine”), from Ancient Greek ἀδᾰμάντῐνος (adămántĭnos, “hard as adamant; made of steel”), from ᾰ̓δᾰμᾰντ- (ădămănt-) (a stem of ἀδάμᾱς…

Etymology from Wiktionary, CC BY-SA 3.0