The Germans made it up. It means "editable crustacean"
crayfish : early 14c., crevis, from O.Fr. crevice "crayfish" (13c., Mod.Fr. écrevisse), probably from Frankish *krebitja or a similar Germanic word that is a dim. form of the root of crab (1); e.g....
They use them to clean
its a crawfish