late 14c., "action of changing," from Old French mutacion (13c.), and directly from Latin mutationem (nominative mutatio) "a changing, alteration, a turn for the worse," noun of action from past participle stem of mutare "to change" (from PIE root *mei- (1) "to change, go, move"). Genetic sense is from 1894. The linguist's i-mutation is attested from 1874; earlier was i-umlaut (1869), from German.
