international rules football vs pigskin

international rules football

noun
  • A sport created as a mixture of Australian rules football and Gaelic football, to allow international matches between Australia and Ireland. 

pigskin

noun
  • A football. 

  • Leather made from the skin of a pig. 

  • The skin of a pig. 

How often have the words international rules football and pigskin occurred in a corpus of books? (source: Google Ngram Viewer )