crown prince vs scion

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. 

scion

noun
  • The heir to a throne. 

  • A detached shoot or twig containing buds from a woody plant, used in grafting; a shoot or twig in a general sense. 

  • A guardian. 

  • A descendant, especially a first-generation descendant of a distinguished family. 

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