Gros Ventre
Pronounced "Grow Vaunt". The word means "big belly" in French. No one knows exactly why the French called them this but take an educated guess. The Gros Ventre were original residents of Minnesota and North Dakota, but as European colonisation pushed them westward, the tribe migrated to Montana, where most of their descendants still live today.
But if all you rootin tootin cowboys are not ready to "go native" then... Gringo as in Johnny.