McLane's entire Rogues Gallery is comprised of villains from a distorted version of American folk history. Liver Eatin' Johnson was a mountain man in the old west who ran afoul of the Crow Nation. Somewhere along here he ate a bunch of their livers to show off how badass he was. This version of him was cursed cursed, so therefore he somehow survived another hundred and fifty years while eating liver after liver. I do have a more elaborate explanation, but that must wait.