propeller vs ventilator

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. 

ventilator

noun
  • A device that circulates fresh air and expels stale or noxious air. 

  • A machine that moves breathable air into and out of the lungs of a patient who is unable to breathe sufficiently. 

  • Some behaviour or happening that relieves a tense atmosphere or situation. 

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