break-off vs perseverence

break-off

verb
  • To play the first shot in a game of snooker 

noun
  • That which breaks off, or is broken off 

  • A break, discontinuance, or interruption 

  • The first shot in a game of snooker or other cue-game 

perseverence

How often have the words break-off and perseverence occurred in a corpus of books? (source: Google Ngram Viewer )