ambergris vs grey amber

ambergris

noun
  • A solid, waxy, flammable substance of a dull grey or blackish color, produced in the intestines of the sperm whale. It is used in perfumes. 

grey amber

noun
  • Used other than figuratively or idiomatically: see grey, amber. 

  • Ambergris. 

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