Is it ensure, insure, or assure?
1861, in reference to musical instruments, past participle adjective from mute (v.). Figuratively by 1879. Of colors by 1939. Related: mutedness.
late 14c., mewet "silent," from Old French muet "dumb, mute" (12c.), diminutive of mut, mo, from Latin mutus "silent, speechless, dumb," probably from imitative base *meue- (cf. Sanskrit mukah "dumb," Greek myein "to be shut," of the mouth). Form assimilated in 16c. to Latin mutus.
1570s, "stage actor in a dumb show;" 1610s as "person who does not speak," from mute (adj.). Musical sense first recorded 1811 of stringed instruments, 1841, of horns.
Unable or unwilling to speak. n.
One who does not have the faculty of speech. No longer in technical use, considered offensive.