double boiler vs roaster

double boiler

noun
  • A pair of interlocking pots, the lower one filled with water which when boiling heats the contents of the upper pot. 

  • A large pan containing hot water, into which other smaller pans are set in order to cook food at low heat (below the boiling point) or to keep food warm. 

roaster

noun
  • A kitchen utensil used for roasting. 

  • A hot Jupiter. 

  • An objectionable person; somebody making a fool of themselves. 

  • A chicken, pig, etc. suitable for roasting. 

  • One who roasts or banters, especially as a comedy routine. 

  • One who roasts food. 

  • A furnace used in making ball soda. 

How often have the words double boiler and roaster occurred in a corpus of books? (source: Google Ngram Viewer )