earl vs prince

earl

noun
  • Any of various nymphalid butterflies of the genus Tanaecia. Other butterflies in this genus are called counts and viscounts. 

  • A British or Irish nobleman next in rank above a viscount and below a marquess; equivalent to a European count. A female using the style is termed a countess. 

prince

noun
  • Any of various nymphalid butterflies of the genus Rohana. 

  • The (male) ruler or head of a principality. 

  • A (male) ruler, a sovereign; a king, monarch. 

  • A type of court card used in tarot cards, the equivalent of the jack. 

  • A non-royal high title of nobility, especially in France and the Holy Roman Empire. 

  • The mushroom Agaricus augustus. 

  • A male member of a royal family other than the ruler; especially (in the United Kingdom) the son or grandson of the monarch. 

  • Someone who is preeminent in their field; a great person. 

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