baroness vs viscount

baroness

noun
  • The wife of a baron. 

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

viscount

noun
  • A member of the peerage, above a baron but below a count or earl. 

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

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