I think French trappers, who paddled the Missouri and Platte rivers beaver trapping, named the Platte. The French word for flat is "plate", so literal translation is "flat water". Don't quote me on that - but I think it's at least close. The Platte is a shallow, meandering, turbid and sandy river in most of Nebraska and only native Nebraskans typically appreciate it's beauty...I guess the same goes for amber waves of grain.