Büchner flask vs Dewar flask

Büchner 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. 

Dewar flask

noun
  • A type of double-walled vacuum flask with silver lining. 

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