In the Old
West, cowboys could be out the
dusty range, for months at a
time, they'd get mighty dirty. So they'd mosey into town with nothing but clothes on their backs and they'd need to wash 'em. So what they'd do is, they would go down to the creek and strip down until they were wearing nothing but their boots. They would keep their
boot on, because of rattlesnakes. In order to warn people who were swimming that the naked cowboy was on his way. He'd yell or call: "Booty", "Booty". Hence "Booty Call"