earl vs peer of the realm

earl

noun
  • 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. 

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

peer of the realm

noun
  • Any similar member of the nobility of other kingdoms. 

  • Any member of the hereditary peerage of the United Kingdom, (chiefly) of the Kingdom of England. 

  • Any member of the House of Lords who is not a life peer. 

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