"cage for birds; place where hawks are put to molt," late 14c., from Old French mue "cage for hawks," especially when molting, from muer "to molt," from Latin mutare "to change" (from PIE root *mei- (1) "to change"). In extended use, "a place of retirement or confinement" (early 15c.). Also as a verb, "to shut up, confine" (mid-15c.).