bathrobe vs dressing gown

bathrobe

noun
  • A robe usually made of terrycloth intended to be worn when one is still damp from bathing or when there is no immediate need to dress fully. 

dressing gown

noun
  • An item of clothing often made from cotton or another absorbent material, in the form of a long open robe with a belt to tie it around the middle and fasten it securely; often worn over pyjamas. 

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