Not to derail this topic by bringing it back on topic, but...
Bill is my real name. I played football in high school, and I was pretty good at it (won state as a sophomore, all-conference my junior year before an injury took away much of my senior year). Anyhow, I would get so worked up before games that my coach started calling me Wild Bill. I also should note that I weighed 240 pounds at the time, could squat over 500, and ran a 4.9 40 yard dash.
I was also the wedgebuster on the kickoff team. The wedge on a return team is a group of five blockers that stand shoulder to shoulder to clear a path for the ball carrier, and my job was to bust through that so that someone else could make a tackle. In the first game of my junior year, I hit the wedge at full speed against one of the smaller schools in our area. I knocked two blockers back so hard that they flew back into the ball carrier, and all three fell on their back with me on top. In essence, I tackled three guys at once, one of whom sustained a concussion.
That's how you earn a nickname.