lethal (adj.)youdaoicibaDictYouDict[lethal 词源字典]
1580s, from Late Latin lethalis, alteration of Latin letalis "deadly, fatal," from letum "death," of uncertain origin. Form altered in Late Latin by association with lethes hydor "water of oblivion" in Hades in Greek mythology, from Greek lethe "forgetfulness."[lethal etymology, lethal origin, 英语词源]