amma vs progenitrix

amma

noun
  • An abbess or spiritual mother, especially one of the Desert Mothers. 

  • mother 

progenitrix

noun
  • A female progenitor, a foremother, any of a person's direct female ancestors (ancestresses). 

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