Yours, Etc.: Origins and Uses of 8 Sign-Offs
1680s, "ear trumpet for the hard-of-hearing," coined from Greek mikros "small" (see mica) + phone "sound" (see fame (n.)). Modern meaning dates from 1929, from use in radio broadcasting and movie recording. Earlier, "amplifying telephone transmitter" (1878). Of the two spellings of the short form of the word, mike (1927) is older than mic (1961).