American football vs footy

American football

noun
  • A game similar to rugby football played on a field of 100 yards long and 53 1/3 yards wide (with two 10 yard-long endzones) in which two teams of 11 players attempt to get an ovoid ball into each other's territory. 

footy

noun
  • The ball used in a game of footy. 

  • A football fan. 

  • Football (association football) (soccer in US, Canada, Australia, New Zealand) 

  • The game or sport of football, usually Australian rules football or rugby league, but not soccer 

  • A short sock. 

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