Barking up the wrong tree

 

When you've planned to accomplish something by using a particular method and your plan is thwarted because you should have gone about it some other way, you've been "barking up the wrong tree."

Hunters have always used dogs to track the whereabouts of their prey.  After chasing the game, the dog often thought it had traced the prospective dinner's flight to a particular tree.  The dog would then bark up that tree.  Its master would hurry over, but sometimes he would find no animal there.  The dog had been, quite literally, "barking up the wrong tree."

This happened with such frequency that the old hunter coined a phrase for it.