We just reversed River Nile to Nile River to make it sound more natural :)

Three things I would like to share: 1. Let’s make this a complete sentence. “People don’t know that…” 2. If you say “a river called Nile” it sounds like you are not referring to the famous river we all know THE Nile. 3. When referring to a river that is well-known, we actually don’t need the word “river”. We can just refer to it by its proper name (ie: the Thames, the Jordan, the Amazon). Just the same as we don’t need other geographic entities to clarify locations (ie: the Atlantic, Everest, or the Andes). Hope this helps!