central heating vs kiln

central heating

noun
  • Any of various heating systems in which a central source of heat is used to distribute heat (and sometimes hot water) throughout a building in a controlled manner. 

kiln

noun
  • An oven or furnace or a heated chamber, for the purpose of hardening, burning, calcining or drying anything; for example, firing ceramics, curing or preserving tobacco, or drying grain. 

verb
  • To bake in a kiln; to fire. 

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