clam vs shellfish

clam

noun
  • A bivalve mollusk of many kinds, especially those that are edible; for example soft-shell clams (Mya arenaria), hard clams (Mercenaria mercenaria), sea clams or hen clam (Spisula solidissima), and other species. The name is said to have been given originally to the Tridacna gigas, a huge East Indian bivalve. 

  • A kind of vise, usually of wood. 

  • One who clams up; a taciturn person, one who refuses to speak. 

  • clamminess; moisture 

  • A vagina. 

  • Strong pincers or forceps. 

  • A dollar. 

  • A crash or clangor made by ringing all the bells of a chime at once. 

  • A Scientologist. 

  • In musicians' parlance, a wrong or misplaced note. 

verb
  • To dig for clams. 

  • To produce, in bellringing, a clam or clangor; to cause to clang. 

  • To be moist or glutinous; to stick; to adhere. 

  • To clog, as with glutinous or viscous matter. 

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 clam and shellfish occurred in a corpus of books? (source: Google Ngram Viewer )