From Middle English
washen,
ywashen (“washed”, past participle of
washen (“to wash”)), from Old English
wascen,
ġewascen (“washed”, past participle of
wascan (“to wash”)), equivalent to
wash +
-en. Cognate with
Dutch gewassen (“washed, washen”),
German gewaschen (“washed, washen”). More at
wash.