[TrainOfThought]

Well, I haven't really had a nickname since I was in ES and HS.
In grade 7-9 I had loads of nicknames based on my last name, which is a very unusual one. Some were alright, others were... not very nice (yes, I was "that fat kid" back then). xD
In HS people called me "Bosse." It's got absolutely nothing to do with my real name (Robin), and I can't quite remember when or how I got that nickname. In Sweden, "Bosse" is usually what you call people with the name Bo. It was completely random, and I still don't get it 5 years later!
... To be honest I don't think the one who gave me the nickname gets it either, so it's all good haha.