Ah, the thread that will reveal my ultra-neardiness.
Anyway, a few years ago I played a role-playing game called Vampire: the Masquerade for the first time. The character I create was a Tremere (simply-put, a clan of magic-casting vampires) and I came up with the name Krendall. I'm sure it was inspired by the fairly popular name Kendall, but I just wanted to tweek it a bit. Anyway, as I got the hang of the game I developed Krendall's personality. He became a very Zen character with a tortured past. It's actually pretty cool and I do plan to finish writing out his history, even though the character himself is dead. At any rate, I liked the character so much I decided to use his name as my Internet persona.
As for why it's MightyKrendall, I tend to add either Mighty at the front of the name or Tremere at the end of the name when just plain Krendall doesn't work. I originally registered as Krendall, but I had trouble getting the password to activate the account. I reregistered as MightyKrendall and, obviously, the account got activated. I've been meaning to ask an admin if I can get the name changed back to Krendall.