vacuum bottle vs vacuum flask

vacuum bottle

noun
  • Synonym of vacuum flask 

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. 

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