latrine (n.)youdaoicibaDictYouDict[latrine 词源字典]
c. 1300, probably from Latin latrina, contraction of lavatrina "washbasin, washroom," from lavatus, past participle of lavare "to wash" (see lave) + -trina, suffix denoting "workplace." Its reappearance in 1640s is probably a re-borrowing from French; especially of a privy of a camp, barracks, college, hospital, etc. Latrine rumor "baseless gossip" (of the kind that spreads in conversations in latrines) is military slang, first recorded 1918.[latrine etymology, latrine origin, 英语词源]
lavatory (n.)youdaoicibaDictYouDict
late 14c., "washbasin," from Latin lavatorium "place for washing," noun use of neuter of adjective lavatorius "pertaining to washing," from lavatus, past participle of lavare "to wash" (see lave). Sense of "washroom" is first attested 1650s; as a euphemism for "toilet, W.C.," it is attested by 1864.