Hadean vs dusky

Hadean

name
  • The Hadean eon; part of the Precambrian supereon, spanning from around 4.6 to 4 billion years ago. 

adj
  • Pertaining to Hades or hell. 

  • Of, or relating to the geological eon. 

dusky

noun
  • A dusky dolphin. 

  • A dusky grouse. 

  • A dusky shark. 

adj
  • Ashen; having a greyish skin coloration. 

  • Dimly lit, as at dusk (evening). 

  • Having a shade of color that is rather dark. 

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