The phrase means to look in the wrong place or accusing the wrong person. The origin of the idiom dates back to early 1800s America, when hunting with packs of dogs was very popular. The term was used literally at first, when wily prey animals such as raccoons would trick dogs into believing they were up a certain tree when in fact they had escaped. Thus, dogs barking at the base of an empty tree were said to be “barking up the wrong tree.”