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.
feeble
feeble-minded
feebleness
feebly
feed
feedback
feeder
feeding
fee-faw-fum
feel
feeler