bowser vs tank truck

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. 

tank truck

noun
  • tanker (type of truck) 

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