crawfish vs crustacean

crawfish

noun
  • Various marine crustaceans, rock lobster; especially Jasus lalandii, the Cape crawfish. 

  • Various freshwater crustaceans, crayfish. 

  • A slur against Anglo-Canadians used in some corners of Quebec (including the Gaspé). 

verb
  • To backpedal, desert or withdraw (also used with out). 

crustacean

noun
  • Any arthropod of the subphylum Crustacea, including lobsters, crabs, shrimp, barnacles and woodlice. 

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