The term 'Lower World River' is a reference to the mythological river Styx, which is a four-letter word. In Greek mythology, the Styx was a river that formed the boundary between the Earth and the Underworld. It was said to be a fast-flowing river of death and hatred, and it was believed that those who drank from it would forget their past lives. The gods of the Underworld swore all their oaths upon the waters of the Styx.