plimsoll vs tennis shoe

plimsoll

noun
  • A rubber-soled lace-up canvas shoe for sports or onboard ships; a precursor of trainers. 

  • The plimsoll symbol ⦵ (or o) that is used as a superscript in the notation of thermodynamics to indicate an arbitrarily chosen non-zero reference point. 

tennis shoe

noun
  • A sneaker (trainer). 

  • A specialty sports shoe designed for playing tennis. 

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