Hehehhehehe a bit of a long story... I play this game called "X-Com"... a turn-based tactical game where you defend the earth from aliens. Well in the sequel to X-Com, Terror From the Deep, it's much, much, much harder... and very easy to run outta ammo if you're not prepared. Luckily, in both of these games there's an weapon called the "stun rod"; it's like a high-tech cattle prod used to capture aliens alive for research purposes.
So what happened was one day I was in a particularly long and difficult mission... all of my soldier's fancy guns had run out of ammo, but the few aliens remaining still had plenty. So what I did was take this one guy who happened to have a stun rod on him and sweep through the entire city... using my other men as decoys, I kept sneaking up behind aliens and knocking em out cold until I completed the mission. I said to my brother, who was watching me, something like "noone can oppose the wrath of STUNLORD!". I immediately renamed him to Stunlord after that. From then on I always had a soldier on my squad named stunlord, who carried one of these rods.
For some reason I liked this name. Eventually I started using Stun instead of Stunlord, also for some unknown reason.