I've had a nickname since I was just a few months old. I was born with torticollis caused by scar tissue on my neck muscles. I had surgery at 6 weeks old to correct the problem and don't have many residual physical effects (except not being able to turn my head all the way to the left). The emotional toll, on the other hand...
The doctor who prescribed my medication following surgery had typically bad doctor handwriting. The pharmacist interpreted my first name as Mania and printed that on my prescription bottles. My parents and their friends thought the error was hilarious, but didn't think too much of it until one day when the pharmacy tech asked, "Is your daughter's name really Mania?" From that day forward my parents, siblings, uncles, and cousins have called me Mania. This nickname, though, is really the most mild of all the nicknames I've had over the years.
Barfia--I'm really not sure how this started, but my cousins still call me this one. It makes me laugh!
Maria Diarrhea/Gonorrhea--The unfortunate side effect of having a name that rhymes with diseases, I suppose.
Hippo Eater--I have absolutely no idea how I got this gem of a nickname, but it was endlessly traumatizing to me as a 4th-grader.
Captain Ducky--My feet turn out a little bit (a LOT) when I walk. My high school friends gave me this one. In fact, with the advent of Facebook, this one has returned with a vengeance.