overlordship vs suzerainty

overlordship

noun
  • The position or quality of being an overlord. 

  • The realm of overlords. 

suzerainty

noun
  • The status or power of a suzerain. 

  • A relation between states in which a subservient nation has its own government, but is unable to take international action independent of the superior state; a similar relationship between other entities. 

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