geyser vs steam generator

geyser

noun
  • A domestic water boiler. 

  • A boiling natural spring which throws forth jets of water, mud, etc., at frequent intervals, driven upwards by the expansive power of steam. 

  • A momentary vertical jet or fountain of fluid driven upwards by a violent force. 

verb
  • To (cause to) rush or burst upward like water from a geyser. 

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 geyser and steam generator occurred in a corpus of books? (source: Google Ngram Viewer )