late 15c., with -y (2) + ware, from Old English wær "prudent, aware, alert, wary," from Proto-Germanic *waraz (source also of Old Norse varr "attentive," Gothic wars "cautious," Old Saxon giwar, Middle Dutch gheware, Old High German giwar, German gewahr "aware"), from PIE root *wer- (3) "perceive, watch out for." Related: Warily; wariness.
Old English wesan, wæs, wæron 1st and 3rd person singular of wesan "to remain," from Proto-Germanic *wesanan (source also of Old Saxon wesan, Old Norse vesa, Old Frisian wesa, Middle Dutch wesen, Dutch wezen, Old High German wesen "being, existence," Gothic wisan "to be"), from PIE root *wes- (3) "remain, abide, live, dwell" (cognates Sanskrit vasati "he dwells, stays;" compare vestal). Wesan was a distinct verb in Old English, but it came to supply the past tense of am. This probably began to develop in Proto-Germanic, because it is also the case in Gothic and Old Norse. See be.
Used mainly of clothes in Old English (the principal verb for washing the body, dishes, etc. being þwean). Old French gaschier "to stain, soil; soak, wash" (Modern French gâcher) is from Frankish *waskan, from the same Germanic source. Italian guazzare also is a Germanic loan-word. To wash (one's) hands of something is 1550s, from Pilate in Matthew xxvii.24. To wash up "clean utensils after a meal" is from 1751. Washed up "no longer effective" is 1923, theater slang, from notion of washing up at the end of a job.