cooker vs immersion heater

cooker

noun
  • A device for heating food, a stove. 

  • A person who is cooked; a crazy person. 

  • A person who makes or uses illicit drugs, especially methamphetamine or cannabis. 

  • An appliance or utensil for cooking food. 

  • A cooking apple. 

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 cooker and immersion heater occurred in a corpus of books? (source: Google Ngram Viewer )