kingship vs regnum

kingship

noun
  • A monarchy. 

  • The territory or dominion of a king; a kingdom. 

  • The dignity, rank or office of a king; the state of being a king. 

regnum

noun
  • A badge of royalty, especially the early form of the pope's tiara. 

  • A rank in the classification of organisms, below dominium and above divisio. 

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