dusty vs nigrescent

dusty

adj
  • Grey in parts. 

  • Covered with dust. 

  • Powdery and resembling dust. 

  • Old; outdated; stuffily traditional. 

  • Ugly, disgusting (a general term of abuse) 

  • ugly, unwell, inadequate, bad (generally used in the negative) 

nigrescent

adj
  • Approaching blackness; blackish, dark-coloured. 

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