adusk vs darkling

adusk

adj
  • Resembling conditions at dusk or twilight, low-lit, dark; in darkness, gloomy. 

adv
  • At dusk; in the dusk or twilight. 

darkling

adj
  • Dark; growing dark; darkening. 

  • Obscure; taking place unseen, as if in the dark. 

adv
  • In the dark; in obscurity. 

noun
  • A creature that lives in the dark. 

  • Darkness 

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