a word applied to killer whales and other large, dolphin-like creatures, 1590s, earlier graundepose (1520s), altered (by influence of grand) from Middle English graspeys (late 13c.), from Anglo-French grampais, from Old French graspois, craspois "whale, (salted) whale meat; blubber; seal," from Medieval Latin craspicis, literally "great fish" or "fat fish," from Latin crassus "thick" (which is of unknown origin) + piscis "fish" (from PIE root *pisk- "a fish"). For specifics of usage in English, see OED.

Proto-Indo-European root meaning "a fish."

It forms all or part of: fish; fishnet; grampus; piscatory; Pisces; piscine; porpoise.

It is the hypothetical source of/evidence for its existence is provided by: Latin piscis (source of Italian pesce, French poisson, Spanish pez, Welsh pysgodyn, Breton pesk); Old Irish iasc; Old English fisc, Old Norse fiskr, Gothic fisks.