omen vs warning

omen

noun
  • Something which portends or is perceived to portend either a good or evil event or circumstance in the future, or which causes a foreboding; a portent or augury. 

  • A thing of prophetic significance. 

verb
  • To divine or predict from omens. 

  • To be an omen of. 

warning

noun
  • Something spoken or written that is intended to warn. 

  • The action of the verb warn; an instance of warning someone. 

intj
  • Used to warn of danger in signs and notices. 

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