harbinger vs warning

harbinger

noun
  • A person or thing that foreshadows or foretells the coming of someone or something. 

verb
  • To announce or precede; to be a harbinger 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 harbinger and warning occurred in a corpus of books? (source: Google Ngram Viewer )