baroness vs earl

baroness

noun
  • A woman holding a baronial title in her own right; a female ruler of a barony. 

  • The wife of a baron. 

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. 

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