Mine is the Spanish name for a kind of bird which happens to be my name in English. Comprende?
Yeah, yeah, tell us another one. Nobody’s fooled. We all know that Ambivalid is just a typo for AmbiviLAD, and that you’re the sole (remaining) member of the Justice League who fights for truth & liberty from a wheelchair. 
Mine is self-explanatory. I like scooters. I own one and I like to ride. It used to be “la cortadora” when I first came on to SD. I asked for it to be changed. La cortadora is a way of saying “nibbler” in Spanish…which is the name of a painting that I own and love.
Couldn’t think of anything at the time, so I went the tried and true, if unoriginal, way and used the names of the cats.
Here is the obligatory picture: Reggie and Hobbes
I chose a username that would immediately communicate to people “Hey, this guy is incredibly clever and probably very good-looking.”
Ok - possible graduate thesis in psych in the works here… someone should do a multiple regression on names, reasons, gender, maybe age, literature references, etc. Hmmmm…what can we learn from this?
I always wanted a clever username, and I’m occasionally clever. But not always, and if the name was too clever I’d probably forget it.
So “Parkhead” is a reference to my preferred Scottish soccer team and “Paul” is, well, my name. Safe, and avoids taxing my own intelligence.
It was a dark and stormy night, three years ago. I came to make an expert comment in an ongoing feud regarding the accuracy of a pineapple appearing in the film A Christmas Story. I didn’t expect to stay, but here I am, I still cannot escape. I chose my name because I felt it had a certain noisy relaxed quality. Or maybe it was a quietly noisy relaxed intensity. I cannot remember, it was an eternity ago.
About 8 years ago I was quite the active poster on the Everquest boards. One of our traditions there was a what did you do over the weekend thread every Monday. Around this time I was having a lot of tom and jerry type accidents, and would post about them. We would joke about it, and my antics eventually led to several nicknames, including booboo bear, Accident Prone Man, and Mr. Accident.
When I started posting here I just used the name I was using over there.
Mine is the German form of the name of an ElfQuest elf that I’ve used as a nickname since before I was ever on the internet. Er, the original elf’s name, not the German form. I took the German form because the original name was taken years ago and immediately abandoned, apparently.
It’s nym I’ve used all over the 'net since my callow and hubristic youth. I was convinced I did “gno it all”. And was clever enough to spell it with the same consonant combination for the English transliteration of the Greek word for knowledge, “gnosis” (γνῶσις). Spelling stuff in classic languages is cool, don’t you gnow? 
Now I’m older, not as callow, and much less hubristic. Wisdom is sometimes knowing how little you know. But I retain the name… partly out of a sense of continuity of identity, and partly ironic reminder.
Took my dog’s name. She’s a blue merle Australian shepherd officially named Waltzing Matilda Blue, but we call her Mattie Blue. She was sitting beside me when I joined.
I’m not the cleverest at this naming stuff.
Mine is from a Frank Zappa song off the Joe’s Garage album, which my dad loves and gave me a copy of when I was in high school. We sing it to each other a lot. Happy thoughts of my awesome dad always come up when I sign in.
Mildly interesting coincidence that the very next poster’s name is also from a Zappa song. I don’t remember if it’s the title or a lyric (it’s not an album of his that I like or even own anymore), but I always liked the word combination. Joining these here messageboards gave me the chance to use it.
“The moving finger writes, and having writ
moves on, nor all your piety and wit
can call it back to change a single line
nor all your tears wash out a word of it.”
Poem by I forget who.
My parents went on their second honeymoon to Hawaii sometime back in the late '90s/early '00s. And All I Got Was This Stupid Keychain, which had my Hawaiian name-- Eke-- derived from my real name. At the time, dolphins were my favorite animal, so it was eke, dolphin.
(Nowadays, foxes are my favorite animal. And before I liked dolphins, I was all about penguins.)
One of my favorite songs by Manu Chao repeats the lyric “Mufatango!!” over and over. There is no literal translation for the word. Argentinian slang uses the word “mufa” sometimes, to mean bad vibes, bad luck, unpleasantness. Still, even my hippest Argentine friends had never heard the word outside of the song. I think Manu Chao coined it, but whether it means the necessity of dancing around bad luck or the constant back and forth of dealing with a two-faced person, or something else entirely… I don’t think anyone knows. I’ve seen multi-page forums dedicated to trying to decipher the meaning.
In addition to the catchiness of the song, I loved the enigma of the word.