I'm using a Macbook Pro and I'm wondering how to change the short name of the "user account"?
I am not sure whether this is what you are after, but by dropping into
Apple has a KB article explaining how the short name as well as the directory name for a user can be changed.
I will cite the instructions to change the short name from the article for versions of OS X 10.5 and later:
If your Mac was a school, a Standard User would be equal to a student, an Administrator would be equal to a Teacher, and root would be equal to the Principal. You can add, move, and delete files without the system complaining much because you're the Boss.
Of course, this means you can screw things up royally. Be careful.
This is Apple's article on how to enable Root: http://support.apple.com/kb/ht1528
I hope that helps!