crepusculum vs smokefall

crepusculum

noun
  • crepuscule; twilight; dusk 

smokefall

noun
  • The close of the day before nightfall, when fog comes. 

  • An artificial waterfall of smoke for shows. 

  • The soot fallout from a cloud of smoke. 

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