Canadian football vs rugby union

Canadian football

noun
  • A game similar to American football played on a field of 110 yards long and 65 yards wide (with two 20 yard-long endzones) in which two teams of 12 players attempt to get an ovoid ball to the end of each other's territory. 

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 Canadian football and rugby union occurred in a corpus of books? (source: Google Ngram Viewer )