It is a product of Gwangyang in South Korea. Cao Cao, the great general and the leader in ancient China, once was on a journey where his soldiers got thirsty and exhausted. He explained that over the hill ahead there would be a plum orchard, and he would let them to eat to their hearts content. The soldiers instantly thought about the plum and the sour taste of it. That made their mouths water, and they forgot their thirst.