Not street or military. It was just something I threw together on the game Runescape which was my first experience 10 years ago or so online with other players. It was a username that just stuck because the name is quite literally who I am and it's simplistic to say. K D just rolls right off the tongue, gets my attention quick and allows other players to relay callouts in game quicker than saying something like "Dire Wolf 82" or any other longer winded usernames. It just works.