railroad truck vs wagon

railroad truck

noun
  • A chassis or framework-like structure underneath a railroad car to which wheel axles (and, hence, wheels) are attached through bearings. (Not to be confused with railway truck or railtruck, which are British English synonyms of railroad car) 

wagon

noun
  • A vehicle (wagon) designed to transport goods or people on railway. 

  • A kind of prefix used in de Bruijn notation. 

  • Buttocks. 

  • A heavier four-wheeled (normally horse-drawn) vehicle designed to carry goods (or sometimes people). 

verb
  • To load into a wagon in preparation for transportation; to transport by means of a wagon. 

  • To travel in a wagon. 

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