crayfish (n.)
"small, freshwater lobster," early 14c., crevis, from Old French crevice "crayfish" (13c., Modern French écrevisse), probably from Frankish *krebitja or a similar Germanic word that is a diminutive form of the root of crab (n.1); compare Old High German krebiz "crab, shellfish," German Krebs. Modern spelling is 16c., under influence of fish (n.).