This idiom means to make a mistake by targeting the wrong person, thing, or approach, often due to a misunderstanding or misjudgment. It suggests pursuing a futile or incorrect course of action, typically used in contexts of blame, accusations, or misguided efforts.

The phrase comes from 19th-century American hunting, where dogs would bark at the base of a tree, mistakenly thinking their prey (like a raccoon) was there when it had escaped. The earliest known use is in James Kirke Paulding’s 1832 *Westward Ho!*: ‘You’re barking up the wrong tree.’ Popularized in frontier literature and newspapers, it reflected rural life and became a staple in American English, later spreading to British usage.