anchoress vs prioress

anchoress

noun
  • A female anchorite. A woman who chooses to withdraw from the world to live a solitary life of prayer and contemplation. 

  • An anchorwoman. 

prioress

noun
  • A nun in charge of a priory (usually lower in rank than an abbess); mother superior. 

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