Sister vs black friar

Sister

noun
  • Title of respect for an adult female member of a fraternal/sororal organization, or comrade in a movement, or even a stranger using fictive kin. 

  • A title used to personify or respectfully refer to concepts or animals. 

  • Title of respect for an adult female member of a religious order. 

black friar

noun
  • A member of the religious order of the Dominicans. 

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