"causing or resulting in death," 1580s, from Late Latin lethalis, alteration of Latin letalis "deadly, fatal," from lethum/letum "death," a word of uncertain origin. According to de Vaan, from Proto-Italic *leto-, which is perhaps a noun from a PIE past participle of a verb meaning "let, let go," on the notion of death as "a letting go." If so, related to Old Church Slavonic leto "summer, year" (from notion of "going"), Russian leto "summer," (pl.) "age, years;" Russian let' (archaic) "it is possible, allowed;" Old Norse lað, Old English læð "land," Gothic unleds "poor."
遗忘是致命的。
来自拉丁语letum,死亡，词源不详。可能同Lethe,冥河，地狱，引申词义死去的，致命的。