international rules football vs rugby union

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. 

rugby union

noun
  • A form of rugby football, historically amateur, having 15 players per side; points are scored for a try, penalty, drop kick or conversion. 

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