microphone (n.)

1680s, "ear trumpet for the hard-of-hearing," coined from Greek mikros "small" (see micro-) + phōnē "sound," from PIE root *bha- (2) "to speak, tell, say." The notion is "instrument for augmenting small sounds." Modern sense of "transducer that converts sound into an electrical signal" is by 1924 in radio broadcasting and movie recording, from the earlier sense "amplifying telephone transmitter" (1878). Of the two spellings of the short form of the word, mike (1924) is older than mic (1961). Related: Microphonic; microphony.