fibula vs heel bone

fibula

noun
  • The smaller of the two bones in the lower leg. 

  • An ancient kind of brooch used to hold clothing together, similar in function to the modern safety pin. 

heel bone

noun
  • The large bone making up the heel of the human foot. 

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