grand duchess vs grand dukedom

grand duchess

noun
  • The wife or widow of a grand duke. 

  • A daughter or granddaughter of a sovereign (czar or later emperor) of the Russian Empire or a pretender to the throne thereof. 

  • The wife of a grand prince. 

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 grand duchess and grand dukedom occurred in a corpus of books? (source: Google Ngram Viewer )