Mine is from the classic Lewis Carroll comedic poem "The Hunting of the Snark". A boojum is a particular type of snark, and anyone who sees one will "softly and suddenly vanish away, and never be heard from again."
For a long time, I used the handle Torque, which I picked up from an item in the Middle Earth: The Wizards CCG called the Torque of Hues. Since my last name is Hughes, my friends started calling me Torque and I stuck with it for several years. However, a year or so ago, I decided to switch to something else for a couple of reasons: I hadn't played the game it was from in several years, and the word had acquired too many bad associations (there was a really bad-looking movie called Torque, and a serial killer in a video game had the same name as well).