harbinger vs lead-in

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. 

lead-in

noun
  • An introduction; something that leads into the beginning of something. 

  • A short phrase that begins the caption of a photograph. 

  • A region of data at the beginning of a compact disc, holding the table of contents. 

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