geyser vs immersion heater

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. 

immersion heater

noun
  • A device for supplying domestic hot water in which a thermostatically-controlled heating element is immersed within a tank of water 

How often have the words geyser and immersion heater occurred in a corpus of books? (source: Google Ngram Viewer )