murderball vs wheelchair rugby

murderball

noun
  • Wheelchair rugby. 

  • A team sport resembling dodgeball in which players are eliminated ("murdered") by being struck with the ball. 

wheelchair rugby

noun
  • A variation of rugby played by players in wheelchairs, primarily players with some disability. It is a full-contact sport and is played on a hardwood court with a ball similar to a basketball. 

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