football field vs international rules football

football field

noun
  • A playing field on which the game of Association football is played. 

  • An informal unit of measure of area, equal to the area of an American football field (57,600 square feet or 1.32 acres). 

  • A playing field on which the game of American football is played. 

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. 

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