propeller vs wind generator

propeller

noun
  • A mechanical device with evenly-shaped blades that turn on a shaft to push against air or water, especially one used to propel an aircraft or boat. 

  • One who, or that which, propels. 

  • A steamboat thus propelled; a screw steamer. 

  • A spinnerbait. 

wind generator

noun
  • a wind-driven generator, working on the same principle as a wind turbine but usually on a smaller scale, used for example for charging batteries on sailing boats. 

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