One god under two names, across The Etruscan World and The Roman Inheritance.
Voltumnavol-tum-naChief God of the Etruscan League — at whose sanctuary the Twelve Cities metThe Etruscan WorldVertumnusver-tum-nusGod of Changing Seasons and TransformationsThe Roman Inheritance
Why the sources call them one god
his Etruscan name was Voltumna, the chief god of the Etruscan league