I came up with that nickname at the age of 16 (in the year 2000). It is supposed to be a random sequence of letters that is pronounceable in German. A search gave no results, hence I naively suspected it to be unique. Only much later I learnt that many sequences of letters humans are able to pronounce do also bear a meaning in some language. Last year I learnt that xixi means piss in Portuguese. Some native English speakers also asked me if it is supposed to mean sexy dude. But I can assure you that I never intended my nickname to signal a sexy dude who takes a piss and casually tries drugs. I was rather annoyed that many nicknames were already taken when I tried to register with various services. I also wanted to be uniquely identifiable. It pretty much worked, as almost all of the 46.100 results of a Google search for xixidu are related to myself.