football field vs rugby league

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. 

rugby league

noun
  • A version of rugby football, played between two teams of thirteen. 

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