duchess vs peeress

duchess

noun
  • The female ruler of a duchy. 

  • The wife or widow of a duke. 

verb
  • to court or curry favour for political or business advantage; to flatter obsequiously. 

peeress

noun
  • A woman holding a noble title in her own right. 

  • A noblewoman married to a peer. 

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