oven vs steam generator

oven

noun
  • A chamber used for baking or heating. 

verb
  • To cook in an oven (colloquial and informal usage only) 

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. 

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