bowser vs tankist

bowser

noun
  • A road vehicle (often a trailer) for the transport of liquid fuel, particularly aviation fuel at an airfield. 

  • A buffoon or imbecile. 

  • A fuel metering/delivery pump at a filling station. 

  • A mobile water tank deployed to distribute fresh water in emergency situations where the normal system of piped distribution has broken down or is insufficient. 

tankist

noun
  • A tanker. 

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