Sheridan's horse, revisited

Thanks to the reader who sent this link to the Smithsonian's Rienzi page.

While we're at it, here's a picture of the opera Rienzi being performed, and another of Rienzi, Missisippi (its graveyard).

Now if anyone can pinpoint the origin of the town's name, we'll be able to close the book on Sheridan's horse.