Rooted in Cornish folklore brought to American mining towns, Tommyknockers are said to be small, ghostly miners who haunt tunnels and shafts. In Colorado, Pennsylvania, and West Virginia, miners claimed to hear phantom knocking on the rock walls — sometimes a warning of cave-ins, sometimes an omen of death. Descriptions range from mischievous dwarf-like figures with lanterns to invisible presences that steal tools or food. Many miners left offerings to appease them, and some blamed disasters on angering the spirits.