headship vs potentate

headship

noun
  • The position of a head or chief. 

  • The position of a headmaster or headmistress. 

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 headship and potentate occurred in a corpus of books? (source: Google Ngram Viewer )