Jerba came in to being back in 1998 or so when I joined the Decipher SWCCG boards. A Jerba, in Star Wars, is a four legged beast of burden. You can see one in front of the Cantina in Star Wars ep. 4. It is also a reference to where George Lucas filmed Star Wars IV's Tatooine scenes on the Tunisian island of Djerba, which transliterated into English is often Jerba.
The reason I chose it? It sounded good, was a Star Wars reference, and it began with J like my name.
I have actually phased out Jerba for the most part, except for use on the SWCCG, LOTRTCG, and Crimson Skies boards. My other name is usually Tervlon. Which I randomly typed one day and decided i liked it.