vacuum flask vs water bottle

vacuum flask

noun
  • A type of glass flask used in a laboratory similar to an Erlenmeyer flask, but with a side spout used for connection to an aspirator. 

  • Synonym of thermos 

  • A Dewar vessel, a scientific instrument used to store liquified gases. 

water bottle

noun
  • A bottle used for carrying water or other drinks. 

How often have the words vacuum flask and water bottle occurred in a corpus of books? (source: Google Ngram Viewer )