Bark/Barking up the wrong tree

To bark up the wrong tree is originally an American expression that dates from the early 19th century for any endeavour that has run off course, and is therefore a fruitless quest. Its origin derives from hunting with dogs. Raccoons, bears and other hunted prey would often shelter in trees. Hunting dogs that were barking up the wrong tree were off the scent. See also On the right/wrong track and Wrong end of the stick.