black coal vs charcoal

black coal

noun
  • coal 

  • high-quality coal 

charcoal

noun
  • A drawing made with charcoal. 

  • impure carbon obtained by destructive distillation of wood or other organic matter, that is, heating it in the absence of oxygen. 

  • A stick of black carbon material used for drawing. 

  • A very dark gray colour. 

adj
  • Made of charcoal. 

  • Of a dark gray colour. 

verb
  • To cook over charcoal. 

  • To draw with charcoal. 

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