Duke vs king of kings

Duke

name
  • The title of a duke. 

  • A male nickname 

  • The American actor John Wayne. 

  • A male given name from English; mostly US and rather rare. 

  • A surname originating as an occupation for service in the household of a duke, or from a nickname. 

king of kings

name
  • The title of an individual king who has other kings as subjects; in particular 

  • Jesus Christ. 

noun
  • A king who has other kings as subjects; an emperor. 

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