caesar vs crown prince

caesar

noun
  • emperor, ruler, dictator 

  • Any agaric mushroom of the genus Amanita, section Amanita sect. Caesareae. 

crown prince

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

  • 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 king. 

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