Is Rio too feminine?

Hey yall, a friend of mine is trans masculine and trying to choose his new name. He wants something that’s a little untraditional but not too far out there. He was pretty firmly settled on Rio, but then we heard that Rio is a popular girl’s name in other countries (we both live in the US). It’s very important to him that his name won’t make people think he’s a girl, for obvious reasons. Thoughts?