lavatory (n.) Look up lavatory at Dictionary.com
late 14c., "washbasin," from Late Latin lavatorium "place for washing," noun use of neuter of Latin adjective lavatorius "pertaining to washing," from lavat-, past participle stem of lavare "to wash," from PIE root *leue- "to wash." Sense of "washroom" is first attested 1650s; as a euphemism for "toilet, W.C.," it is attested by 1864. Related: Lavatorial.