Canadian football vs VFL

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. 

VFL

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