entr'acte vs interregnum

entr'acte

noun
  • An interval between two acts of a play or opera. 

  • Another performance, such as a piece of music or a dance, during this. 

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 entr'acte and interregnum occurred in a corpus of books? (source: Google Ngram Viewer )