harbinger vs pole star

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. 

pole star

noun
  • A person, principle, or thing which acts as a guide; a guiding light; also, something which attracts much attention; a centre of attention. 

  • The star visible to the naked eye which was in the past, is now, or will be in the future nearest a celestial pole of a planet. 

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