Have you ever done something that is wrong or made an incorrect assumption?
If so, then you were barking up the wrong tree.
This phrase comes from a dog chasing an animal up a tree.
The animal escapes to a different tree but the dog is still barking up the same tree, even though it’s empty.
You’re likely to hear this phrase in police dramas.
The police thought they were pursuing the correct suspect, but they were barking up the wrong tree.
If she thinks I’m going to help her, she’s barking up the wrong tree.
I was barking up the wrong tree when I asked him to come on time. He’s always late.