blue blood vs viscount

blue blood

noun
  • An aristocrat. 

  • Noble or aristocratic ancestry. 

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 blue blood and viscount occurred in a corpus of books? (source: Google Ngram Viewer )