ball game vs rugby ball

ball game

noun
  • Any game played with a ball. 

  • A decisive outcome in regard to some ongoing situation; game over. 

  • Affair, issue, matter, subject, story, topic. 

  • A specific contest or match between teams playing such a game, in particular a baseball game. 

  • A sport played in the Aztec and Mayan civilizations; Mesoamerican ballgame. 

rugby ball

noun
  • A spheroidal ball designed for the sport of rugby. 

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