Elbow grease is an old term for working hard at manual labour or trades, as in "put some elbow grease into that".
It has also been used as a practical joke by master tradesperson on apprentices, e.g. "Go fetch some elbow grease from him". Each tradesperson will say someone else has the elbow grease and send the unwitting apprentice on to another master tradesperson. The snipe hunt will continue until the apprentice gives up, catches on or runs out of people/places to search.