geyser vs water 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. 

water heater

noun
  • An appliance for heating water above its ambient temperature, generally for domestic use. 

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