A statistically insignificant number of people are named North and Apple, too, but we wouldn't allow those here either. Unless a common noun is a far more common name, it really doesn't sound like a name, sorry.
I would generally not accept 2 names sharing a basis in nature. Alex Leafwind would be fine, Pond Stargazer for example would also be fine. River Leafwind just sounds like you're looking outside and naming things that you see.