crown princess vs scion

crown princess

noun
  • The heiress apparent to the throne in a royal or imperial monarchy. 

  • The wife of a crown prince. 

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 princess and scion occurred in a corpus of books? (source: Google Ngram Viewer )