murk vs pitch-black

murk

adj
  • Dark, murky 

noun
  • Darkness, or a dark or gloomy environment. 

verb
  • To murder or seriously injure. 

  • To make murky or be murky; to cloud or obscure, or to be clouded or obscured. 

pitch-black

adj
  • Very dark; without light. 

How often have the words murk and pitch-black occurred in a corpus of books? (source: Google Ngram Viewer )