drone
n.
Old English dran, dræn "male honeybee," from Proto-Germanic *dran- (cognates: Middle Dutch drane; Old High German treno; German Drohne, which is from Middle Low German drone), probably imitative; given a figurative sense of "idler, lazy worker" (male bees make no honey) 1520s. Meaning "pilotless aircraft" is from 1946.
Drones, as the radio-controlled craft are called, have many potentialities, civilian and military. Some day huge mother ships may guide fleets of long-distance, cargo-carrying airplanes across continents and oceans. Long-range drones armed with atomic bombs could be flown by accompanying mother ships to their targets and in for perfect hits. ["Popular Science," November, 1946]
Meaning "deep, continuous humming sound" is early 16c., apparently imitative (compare threnody). The verb in the sound sense is early 16c.; it often is the characteristic sound of airplane engines. Related: Droned; droning.