cordwood vs firewood

cordwood

noun
  • Wood suitable for use as firewood; firewood cut and split into conveniently sized pieces for easy stacking into cords. 

  • Split and cut wood as an economic commodity. 

firewood

noun
  • Wood intended to be burned, typically for heat. 

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