dynamo vs idler

dynamo

noun
  • An electricity generator; a dynamo-electric machine. 

  • The mechanism by which a celestial body, such as the Earth or a star, generates a magnetic field. 

  • An energetic person. 

idler

noun
  • One who idles; one who spends his or her time in inaction. 

  • One who idles; a lazy person; a sluggard. 

  • A mechanical device such as a pulley or wheel that does not transmit power, but supports a moving belt etc. 

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