caesura vs interregnum

caesura

noun
  • A break of an era or other measure of history and time; where one era ends and another begins; turning point. 

  • Using two words to divide a metrical foot. 

  • A pause or interruption in a poem, music, building, or other work of art. 

  • The caesura mark ‖ or ||. 

interregnum

noun
  • 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. 

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

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