Toil means to work hard and long; exhausting physical labor. Useless toil is present in both the myth and the modern story because in the myth, the deceitful king works so hard to roll the boulder up to the top of the hill only for it to roll back down again. In the modern story, the fisherman works so hard to reel in an enormous fish, only for sharks to eat it before he can get it to shore. In both cases, they are working hard for no personal gain.
