augury vs death knell

augury

noun
  • An omen or prediction; a foreboding; a prophecy. 

  • A divination based on the appearance and behaviour of animals. 

  • An event that is experienced as indicating important things to come. 

death knell

noun
  • A sign or omen foretelling the death or destruction of something. 

  • The tolling of a bell announcing death. 

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