caesura vs interstice

caesura

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

  • Using two words to divide a metrical foot. 

  • The caesura mark ‖ or ||. 

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

interstice

noun
  • A fragment of space. 

  • A small opening or space between objects, especially adjacent objects or objects set closely together, as between cords in a rope or components of a multiconductor electrical cable or between atoms in a crystal. 

  • A small interval of time free to be spent on activities other than one's primary goal. 

  • An interval of time required by the Roman Catholic Church between the attainment of different degrees of an order. 

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