Kinda boring, but in college I was dubbed "Wild Bill" for, well, a bit of a less than rational streak when pushed into a corner.
Then later on that evolved into "Flash" in the 1980's. I was a machinist/tool & die maker and in our shop we would play practical jokes on each other. I, uh was gettin' even with one of the welders and while he was at lunch I put an M80 under a big piece of steel (part of a conveyer) he was welding. He came back, started welding and you can guess the rest!
Later on in the 90's I got together with some of my old buds from college and apparently I was still the same crazy bas***d they knew then so, they started calling me...wait for it...StillBill. Been that way ever since. Well, except for a name or two my Wife as come up with over the years...but I won't repeat those here.