Barry was always just a nickname; he decided to start using Barack when he started college. We had a friend in college who did the same thing, and it's really confusing to hang out with his friends from high school when they call him Ian all the time, because his real name is Chris.
Editorial note: Whoa! You've found a super-old post here on BuzzFeed, from an earlier era of the site. It doesn't really represent where we are anymore, and may in fact be totally broken, but we're leaving it up as a part of our early history.