locomotor vs power car

locomotor

noun
  • Something that is capable of locomotion. 

adj
  • Of or pertaining to movement or locomotion. 

power car

noun
  • A vehicle equipped with machinery for supplying heat or electrical power to other parts of a train. 

  • A vehicle that propels, and commonly also controls, a passenger train or tram, often as the lead vehicle. 

  • Antonym: trailer car 

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