To waste
energy; to be going after the
wrong thing. The
phrase comes from raccoon hunting, which takes
place in the dark. The
dogs have been
trained to
point out the tree where the raccoon has fled, but they can mistake the tree in the dark and
bark up the
wrong one. (see Brewer) [
ex - If you think I am the one who is going to do that
project for you, you are barking up the
wrong tree.]