Keanu does NOT mean "mist over the mountains." Mist has many translations in Hawaiian; the primary one is "noe." Mountain is "mauna." Keanu is not derived from either of these words.
Being named after some actor because your mom used to think he was hot and being stuck with a foreign-sounding name that hasn't really caught on must suck.
I know it's a real name, but now it would look obvious that the parents using it are obsessed with Keanu Reeves. Celebrity-inspired names like this will totally date the bearer.