caoutchouc vs india rubber

caoutchouc

noun
  • latex; natural rubber 

india rubber

noun
  • The rubber made from this latex. 

  • The latex obtained from certain trees of several families, especially Hevea brasiliensis, widely cultivated in Asia. 

How often have the words caoutchouc and india rubber occurred in a corpus of books? (source: Google Ngram Viewer )