pilon vs tibial plafond

pilon

noun
  • A conical loaf of sugar. 

  • A gratuity given by tradesmen to customers settling their accounts. 

  • A heap of tobacco arranged for fermentation. 

tibial plafond

noun
  • The articular surface of the distal end of the tibia. 

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