"Barking up the wrong tree" means to waste one’s efforts by pursuing the wrong thing or path.

The earliest known printed citation of this phrase is James Kirke Paulding’s Westward Ho!, 1832:

"Here he made a note in his book, and I begun to smoke him for one of those fellows that drive a sort of a trade of making books about old Kentuck and the western country: so I thought I’d set him barking up the wrong tree a little, and I told him some stories that were enough to set the Mississippi a-fire; but he put them all down in his book."

There are at least three answers to where the saying originated. One has the term coming from the nocturnal pursuit of raccoons using hunting dogs. Occasionally a raccoon fools the dogs, which crowd around a tree, barking loudly, not realizing their quarry has taken a different route.

Another is also a hunting reference, but it refers to dogs attempting to tree a bear that doesn’t want to be treed, which can often end badly for the dogs.

And yet another has it as a lumbering term. "Bark up" means to debark a felled tree, which is a bad thing to do prior to hauling since the bark protects the meat of the wood.