1873, an irregular shortening of rotator, originally in mathematics. Mechanical sense of "rotating part of a motor" is attested by 1903; specifically of helicopters from 1930.
Entries linking to rotor
rotator n.
1670s, "muscle which allows a part to be moved circularly," agent noun from Latin rotare "turn round, revolve" (see rotary). Also compare rotor. General mechanical sense of "one who or that which rotates" is by 1772. Related: Rotatory.
Rototiller n.
machine with rotating blades to break up soil, 1923, from roto-, perhaps based on the mechanical use of rotor, + tiller.