"Standback" I took at the age of 12 from a character in a Dragonlance book. Specifically, a gnome in a quite minor short story in one of the early short story collections (when Dragonlance was still any good). Standback was a typical gnome who built a wide variety of brilliant-yet-utterly-useless devices. I liked the name, I liked gnomes, and I needed a screenname; it's worked out pretty well. It's a good name that's nice and memorable with no knowledge of the story or setting (which is very good, because few people know the story and I no longer associate myself with the setting very much
).
I've used it on a Discworld MUD, on the Kencyclopedia where I
ran a contest and
answered gnome questions for a while, and other random places. The only forum in which I
don't go by Standback is on the Israeli Roleplaying Phorums, where I just didn't manage to make "Standback" stick, but suddenly acquired a bit of a reputation as "Zivities", which is what you get when you squash my RL first and last names together (no "W" in Hebrew, it's a "V" sound instead). Hey, whatever sticks.