entr'acte vs halftime

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. 

halftime

noun
  • The halftime show, the primary light entertainment of a game, after the second quarter, when players can physically recover, coaches can give players a pep talk, bets can be doubled, etc. 

How often have the words entr'acte and halftime occurred in a corpus of books? (source: Google Ngram Viewer )