Might as well chime in with my nickname story and refresh the thread in case there are nickname stories as-yet-untold out there in 'Cat Land....
When I first got on the Internet in...*counts on fingers*...1992, one of the first things I discovered was a telnettable Internet BBS in Omaha. I played around with name ideas (Brian Boru among them), but then logged on as Shadowspawn, a character from the Robert Lynn Asprin-edited "Thieves' World" fantasy anthology series, and started posting under that name. Shadowspawn's real name in Sanctuary, the city of "Thieves' World," is Hanse. So on story boards, I'd be "Hanse called Shadowspawn," which soon expanded to "Hanse called Shadowspawn, Saint of the Nether Northern Regions of Morpo and Chosen One of the Huy." (Long story.)
And of course on regular discussion boards, it quickly got shortened to Shad, or as my interest in "Celtic" music became apparent to my friends, mutated into "Shad O'Spawn" and Gaelicized into "Siad ui Span," which was given me by my friend at Queens University Belfast at the time, who said it kind of roughly meant "Daughter of Herring."
As I went to other forums, like ISCA, etc., I found that "Shadowspawn," and often "Shad," was already taken, so I took to other permutations. I'm from South Dakota, so SDShad has kind of been my default login for free email services, newspaper websites, etc., for some time now, so's I'll remember it.
So SDShad I am here as well. All of which you desperately needed to know, I'm sure.