crown prince vs king of kings

crown prince

noun
  • A person designated and raised to become the next king. 

  • A person expected to inherit or take over an enterprise or undertaking once its current manager retires or dies. 

  • A person designated and raised to become the next emperor. 

king of kings

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

name
  • Jesus Christ. 

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

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