I love hearing stories about how people came up with their first internet pseudonym. It tells a lot about a person, especially when the pseudonyms are really nerdy.
My first pseudonym came from watching a lot of Star Trek: Voyager. When I was living in Edinburgh between 1997-1999, I trained in a martial art called Kuk Sool Won. My instructor Master Don Mackenzie used popular TV and movie quotes to motivate us; with many of his references coming from Highlander, Star Trek, and various superhero movies. In Star Trek: Voyager episode Drone, a Borg drone is created after a transporter incident that fuses the Doctor's mobile emitter with some of Seven of Nine's nanoprobes. During the course of the episode the drone asks for a designation, but since Seven of Nine and Captain Janeway are encouraging him to embrace his individuality, he selects the name One. Soon after that episode aired, Master Don started teasing/motivating me by calling me "One of One." I loved it.
When I finally went to register my first email address I tried to get oneofone, but someone had already taken it. As they do, Yahoo suggested I add a number to the username to make it unique. So what number did I add? 5618, the Borg designation for the human species. After that, oneofone5618 was born! :P
So what was your first internet pseudonym, and what was the story behind it?