18-wheeler vs bakkie

18-wheeler

noun
  • A big rig truck: a semi-trailer plus the truck or tractor pulling it. 

bakkie

noun
  • A small pick-up truck or ute, generally open and sometimes fitted with a removable canopy, but distinct from an enclosed van and a large truck. 

  • A small bowl or container, sometimes with a cover such as a Tupperware container. 

How often have the words 18-wheeler and bakkie occurred in a corpus of books? (source: Google Ngram Viewer )