feedback (n.)youdaoicibaDictYouDict[feedback 词源字典]
1920, in the electronics sense, "the return of a fraction of an output signal to the input of an earlier stage," from verbal phrase, from feed (v.) + back (adv.). Transferred use, "information about the results of a process" is attested by 1955.[feedback etymology, feedback origin, 英语词源]
monophonic (adj.)youdaoicibaDictYouDict
of recordings, broadcasts, etc., "not stereo, having only one output signal," 1958, coined to be an opposite of stereophonic; from mono- + -phonic, from Greek phone "sound, voice," from PIE root *bha- (2) "to speak, tell, say" (see fame (n.)).