The Word Detective explains that the phrase probably originated with the Irish “seibin,” which is a small mug. “Shebang” first appears during the Civil War to describe a hut, shed, or some other kind crude makeshift shelter for soldiers. At about the same time “shebang” started being used to mean a vehicle and a rented coach in particular. “Shebang” has also been used to describe a disreputable tavern or hotel that is also called a “dive.” Today it is most commonly used to describe the entire thing or matter.