chassis vs railway carriage

chassis

noun
  • A base frame, or movable railway, along which the carriage of a mounted gun moves backward and forward. 

  • A woman's buttocks. 

  • The base frame of a motor vehicle. 

  • A frame or housing containing electrical or mechanical equipment, such as on a computer. 

railway carriage

noun
  • A railroad car (for passengers) 

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