break-off vs interregnum

break-off

noun
  • A break, discontinuance, or interruption 

  • That which breaks off, or is broken off 

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

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

interregnum

noun
  • An intermission in any order of succession; any breach of continuity in action or influence. 

  • The period of time between the end of a sovereign's reign and the accession of another sovereign. 

  • A period of time during which normal executive leadership is suspended or interrupted. 

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