calefactor vs hotplate

calefactor

noun
  • A heater; one who, or that which, makes hot, such as a stove, etc. 

hotplate

noun
  • A low-powered heating device for keeping food warm. 

  • The element of a stove. 

  • A semi-portable stove. 

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