impeller vs rotor

impeller

noun
  • A rotating component that accelerates fluid outward from a center of rotation, found in devices such as pumps, water jets, washing machines, and agitated tanks. 

  • Something which or someone who impels. 

rotor

noun
  • A rotating part of a mechanical device; for example, in an electric motor, generator, alternator, or pump. 

  • The wing of a helicopter or other rotary-wing aircraft. 

  • A type of powerful horizontal-axis atmospheric vortex generated by the interaction of strong winds with mountainous terrain. 

  • A quantity having magnitude, direction, and position. 

How often have the words impeller and rotor occurred in a corpus of books? (source: Google Ngram Viewer )