LOL, re: name. It is a private joke. But I will let you in on it. It is short for Medium Sized White Guy.
When I was in college I was a bouncer. The group of guys I bounced with had worked together for a few years before I came along. The MdmSzdWhtGuy thing came about before I came along, but it was a famous story and goes like thus:
One of our buddies was a huge black guy we all called "Wolf". Killer cool nickname, real name was Jeff, but that is besides the point. Wolf was 6 feet 6 inches tall, around 300 lbs, but was so athletic even at that size he played shortstop on a big time softball team. Absolute monster of a man. Well, anyways, one night the OU wrestling team comes down to the bar, and the whole squad gets into a fight with the bouncers. Wrestlers are some very tough cats, and it was real tough going, so Wolf, who was not a bouncer, but a friend to many of them, decides he is going to help out.
In the melee, he threw 3 punches and knocked out 3 very tough guys. After the fight settles down (out in the parking lot) he began to walk back inside. As he was walking inside one of the larger wrestlers (still much smaller than Wolf) was walking beside Wolf and mouthing off to him. Rather than turning and facing the guy, Wolf, almost nonchalantly, elbows this wrestler in the side of the head, and drops him like a sack of potatoes.
A buddy of mine, who was bartending at the place and witnessed the event was reagalling myself, and a few compatriots with this story, when one of the listners asked him the following question. "Wasn't Wolf worried when this 220 lb wrestler stepped up to him?"
Bartender's reply "Wolf isn't to impressed by a medium sized white guy"
We all fell out laughing and the phrase stuck. Since I happen to be a medium sized white guy, and love that story so much, I adopted it for my screen name.
There ya have it.
B.