1. If Frank is trying to get a pay raise from the assistant manager, he’s barking up the wrong tree. Only the manager can authorize a pay increase.
2. Janice is angry at me because she thinks I took her books, but she’s barking up the wrong tree I had nothing to do with it.

This expression stems from the 19th century American frontier practice of hunting raccoons using hunting dogs. When the raccoon attempted to escape up a tree, the dog was supposed to remain at the foot of the tree barking until the hunter arrived. However, if the dog went to the wrong tree, especially at night, or the raccoon jumped to the branches of another tree, the hunter would end up focusing on the wrong tree.