Sir vs armiger

Sir

noun
  • The titular prefix given to a knight or baronet. 

armiger

noun
  • Any person entitled to bear a coat of arms. 

  • An esquire, originally carrying the armour of a knight; (hence, later) a man of the gentry ranking below a knight. 

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