double boiler vs kettle

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. 

kettle

noun
  • A vessel for boiling a liquid or cooking food, usually metal and equipped with a lid. 

  • An instance of kettling; a group of protesters or rioters confined in a limited area. 

  • A vessel or appliance used to boil water for the preparation of hot beverages and other foodstuffs. 

  • A kettle hole, sometimes any pothole. 

  • The quantity held by a kettle. 

  • A group of raptors riding a thermal, especially when migrating. 

  • A steam locomotive 

  • A kettledrum. 

verb
  • To contain demonstrators in a confined area. 

  • Of a boiler: to make a whistling sound like the boiling of a kettle, indicative of various types of fault. 

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