It's nothing really exotic (or interesting)...
I started playing World of Warcraft a couple of weeks after it first came out and I wanted a meaningful name for my first character (A Tauren Shaman). My first name is David, and my middle name is Ian, and in university, the IT people apparently had no convention for assigning usernames, so I guess they thought it would be funny [not] to make my login ID "davidian" (the Waco Siege began the same year I started university). I did grow to like the username, but I didn't appreciate the association with the Waco Siege tragedy. The Celtic word for bull is "tarb", so I took part of my old login ID and appended it to tarb to get "Tarbidian" and this is what I called my first WoW character. I kind of liked the name, so I registered the domain name tarbidian.com.