enslave vs play on

enslave

verb
  • To make subservient; to strip one of freedom; enthrall. 

play on

verb
  • To exploit by exacerbating. 

  • to hit the ball into his own wicket, thus being out bowled 

  • Used other than figuratively or idiomatically: see play, on. 

  • to let the game continue after a foul has been committed, because the situation is advantageous to the team who would be awarded a foul. 

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