dynamo vs eager beaver

dynamo

noun
  • An energetic person. 

  • 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. 

eager beaver

noun
  • One (especially a child) who is very excited or enthusiastic to begin a task; a person who is exceedingly assiduous in an enthusiastic manner 

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