masc. proper name, from Old French Gerart (Modern French Gérard), of Germanic origin; compare Old High German Gerhard, literally "strong with the spear," from ger "spear" (see gar) + hart "hard" (from PIE root *kar- "hard").
pike-like fish, 1765, American English, shortening of garfish (mid-15c.), from fish (n.) + Middle English gare, gore "a spear," from Old English gar "spear," from Proto-Germanic *gaisa- "spear" (source also of Old Norse geirr "spear; point of an anvil," Old Saxon, Old High German ger, German Ger "spear"), from PIE *ghaiso- "a stick, spear" (see goad (n.)). The fish so called for its long sharp snout. Compare Edgar, garlic.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit karkatah "crab," karkarah "hard;" Greek kratos "strength," kratys "strong;" "hard;" Old English heard, German hart "solid and firm, not soft."