hotbed vs stoker

hotbed

noun
  • An iron platform in a rolling mill, on which hot bars, rails, etc., are laid to cool. 

  • A low bed of earth covered with glass, and heated with rotting manure, used for the germination of seeds and the growth of tender plants, like a miniature hothouse. 

  • An environment that is ideal for the growth or development of something, especially of something undesirable. 

stoker

noun
  • A device that feeds coal into a furnace, etc., automatically. 

  • A person who stokes, especially one on a steamship or steam train, who stokes coal in the boilers. 

  • A person who pedals on the back of a tandem bicycle. 

  • A device for stoking a fire; a poker. 

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