calefactor vs melter

calefactor

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

melter

noun
  • A laborer who operates such a furnace. 

  • A person or thing that melts. 

  • A furnace used for melting iron in a foundry. 

  • A variety of peach in which the flesh parts freely from the stone when ripe, also known as a free-stone. 

  • An obsolete spelling of milter. 

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