ethnarch vs potentate

ethnarch

noun
  • A leader of an ethnic community, especially a Jewish or (in the Ottoman Empire) Eastern Orthodox leader having political as well as spiritual authority. 

  • The governor of a Jewish province under the Roman Empire. 

potentate

noun
  • A powerful leader; a monarch; a ruler. 

  • A self-important person. 

  • A powerful polity or institution. 

  • Someone acting in an important role. 

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