best man vs harbinger

best man

noun
  • Used other than figuratively or idiomatically: see best, man. 

  • The primary attendant to the groom in a wedding ceremony. 

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. 

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