ambergris vs sperm whale

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. 

sperm whale

noun
  • A whale (Physeter catodon, syn. Physeter macrocephalus), the largest of the toothed whales. 

  • Any whale in the superfamily Physeteroidea, which also includes the small whales of genus Kogia. 

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