washer (n.1)

1520s, "person who washes," agent noun from wash (v.). From 1808 as "machine that washes." Washer-woman is from 1630s; earlier wash-woman (1580s).

washer (n.2)

"flat ring for sealing joints or holding nuts," mid-14c., generally considered an agent noun of wash (v.), but the sense connection is difficult, and the noun may derive instead from the ancestor of French vis "screw, vise" (see vise).