nightrobe vs peignoir

nightrobe

noun
  • A robe to be worn at night; a nightgown. 

peignoir

noun
  • A long outer garment for women, usually sheer and made of chiffon and often sold with matching nightgown, negligee or underwear 

  • A cape worn to protect the clothes at the barbers / hairdressers 

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