crown prince vs heritor

crown prince

noun
  • 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. 

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

heritor

noun
  • A person who inherits; an heir or heiress. 

  • A proprietor or landholder in a parish. 

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