Alternative History: the grand canyon

About the Grand Canyon, USA

Historical evidence shows that John Wesley Powell named it because of the grandeur of it all.

Another view is that fur trappers or other explorers trekked down the Grand River in Colorado that is now known as the Colorado River (renamed by fiat in 1923). They would have known of the canyons of the Grand River far before Powell did and indeed could have spread their story as such which could be something on the order of, "there are spectacular canyons carved out by the Grand River west of Grand Junction". This would not have to have been written down. Just that the story was told and moved by word of mouth back to the east into civilization where it was written down. Once it is written down it can be read by any explorer before they set out on their adventure.

No doubt Powell read everything published about the Green, San Juan, and Colorado rivers and may have come across this tale instilling the concept of a "Immense Canyon(s) on the Grand River"... or the "Grand River Canyon" or the "Grand Canyon".

This is a very old theory and cannot be proven unless some document by some person mentions this large canyon that dozens (100s) of people knew about a century before.

I realize we mush give Powell the honor of naming it if for no other reason than publication but I do not think he would have been offended if asked about his research before the first expedition.

Historians, please... has research been done to find evidence of this idea?