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....
its a crawfish
If it was injured or sick it may see the other as a weakness in its community
Just like any other living thing ... Yes .