dressing gown vs housecoat

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. 

housecoat

noun
  • A longish dress-like garment of one piece, fastening down the front, worn about the house. 

  • A bathrobe or dressing gown. 

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