crepuscle vs dusk

crepuscle

dusk

verb
  • To begin to lose light or whiteness; to grow dusk. 

  • To make dusk. 

adj
  • Tending to darkness or blackness; moderately dark or black; dusky. 

noun
  • A darkish colour. 

  • The condition of being dusky; duskiness 

  • A period of time at the end of day when the sun is below the horizon but before the full onset of night, especially the darker part of twilight. 

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