I thought it was change at random as it says "This option allows you to change your forum username from '_____' to a different username.
At the bottom of New Username box it says "You can change your username once every 1 day and your remaining username changes : 2"
I don't like having my real name in my username. First of all it's dumb, and second of all I don't feel like it's safe. I've shared too much personal information about the area I live in, about my cats and my house, and I don't want my name shared too.