oyster vs shellfish

oyster

noun
  • Any of certain marine bivalve mollusks, especially those of the family Ostreidae (the true oysters), usually found adhering to rocks or other fixed objects in shallow water along the seacoasts, or in brackish water in the mouth of rivers. 

  • A person who keeps secrets. 

  • A shoplifter. 

  • A pale beige color tinted with grey or pink, like that of an oyster. 

  • The delicate morsel of dark meat contained in a small cavity of the bone on each side of the lower part of the back of a fowl. 

adj
  • Of a pale beige colour tinted with grey or pink, like that of an oyster. 

verb
  • To fish for oysters. 

shellfish

noun
  • A fisheries and colloquial term for an aquatic invertebrate having an inner or outer shell, such as a mollusc or crustacean, especially when edible. 

  • A culinary and nutritional term for several groups of non-piscine, non-tetrapod, aquatic animals that are used as a food source. The term often exclusively refers to edible aquatic crustaceans, bivalve mollusks and cephalopod mollusks; but sometimes echinoderms may be included as well. 

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