Mine originates from when I was very wee (middle schoolish) and had not yet discovered that elves often annoyed me. (Books I'm still pretty happy about.)

So it's been 'bookelf' various online places for ages, and I tacked an 'e' on the end for my IM around the same time, since 'bookelf' was taken and I rebel against numbers in name-type things and 'bookelfe' looked, I thought, sort of pretty written out.

And then I was 'bookelfe' on IM, and I was too lazy to think up anything different for my LJ!