an animal of the class Crustacea, 1835; see Crustacea + -an. As an adjective, "of or pertaining to an animal of the class Crustacea," 1858 (an earlier adjective was crustaceous, "pertaining to crust, crust-like," 1640s).
arthropod class, 1814, Modern Latin neuter plural of crustaceus (animalia), literally "having a crust or shell," from Latin crusta "crust, rind, bark, hard shell" (from PIE root *kreus- "to begin to freeze, form a crust;" also see -a (2)). Taken as a zoological classification by Lamarck, 1801; Cuvier (1798) had les insectes crustacées.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit krud- "make hard, thicken;" Avestan xruzdra- "hard;" Greek krystallos "ice, crystal," kryos "icy cold, frost;" Latin crusta "rind, crust, shell, bark;" Lettish kruwesis "frozen mud;" Old High German hrosa "ice, crust;" Old English hruse "earth;" Old Norse hroðr "scurf."
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Definitions of crustacean from WordNet
any mainly aquatic arthropod usually having a segmented body and chitinous exoskeleton;