steam generator vs teakettle

steam generator

noun
  • a type of boiler fitted in a diesel locomotive or another rail vehicle, which provided steam heating in steam-heated passenger trains that had previously been hauled by steam locomotives. 

teakettle

noun
  • A vessel used to boil water for tea or other hot beverages. 

verb
  • To make a shrill sound like a boiling teakettle. 

How often have the words steam generator and teakettle occurred in a corpus of books? (source: Google Ngram Viewer )