rugby vs rugby football

rugby

noun
  • The form of the game known as rugby union (see the usage note). 

  • A form of football in which players can hold or kick an ovoid ball; rugby football. The ball cannot be handled forwards and points are scored by touching the ball to the ground in the area past the opponent's territory or by kicking the ball between goalposts and over a crossbar. 

  • Rubber cement, contact cement. 

verb
  • To play rugby. 

rugby football

noun
  • The sport of rugby: either rugby league or rugby union. 

  • A rugby ball. 

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