baron vs grand prince

baron

noun
  • The male ruler of a barony. 

  • A male member of the lowest rank of English nobility (the equivalent rank in Scotland is lord). 

  • A person of great power in society, especially in business and politics. 

  • A prisoner who gains power and influence by lending or selling goods such as tobacco. 

  • Any of various nymphalid butterflies of the genus Euthalia. 

  • A baron of beef, a cut made up of a double sirloin. 

grand prince

noun
  • An unusual ruler's title, sometimes incorrectly rendered as grand duke, mainly used in Lithuania and some parts of Russia (Muscovy would ultimately unite most Russian principalities and rise to imperial rank) and the Holy Roman Empire. 

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