It was my undergrad email address, my first initial and the first seven letters of my last name. At the time it made perfect since to me, t westerm and I stuck with it, I even have my own twesterm domain.
Boy was that a mistake.
It's amazing how many people get confused by twesterm and think it's twestern. I don't know how people have tried correcting me or get my email address wrong when I fill something out even after I explicitly say yes, that is an m on the end.
I would change it, but I'm lazy and I already have the domain I don't feel like changing. Before twesterm though I used Dr Obvious for most things, but that was the late 90's and early 2000's.