foreboding vs ominous

foreboding

adj
  • Of ominous significance; serving as an ill omen; foretelling of harm or difficulty. 

noun
  • A sense of evil to come. 

  • An evil omen. 

ominous

adj
  • Specifically, giving indication of a coming ill; being an evil omen 

  • Of or pertaining to an omen or to omens; being or exhibiting an omen; significant. 

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