crown prince vs grand dukedom

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. 

grand dukedom

noun
  • The title of grand duke or grand duchess, with its pertaining privileges and obligations; contrast grand duchy. 

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