dowager vs peeress

dowager

noun
  • a widow holding property or title derived from her late husband 

  • any lady of dignified bearing 

peeress

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

  • A noblewoman married to a peer. 

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