Zwaan (dutch for swan)
I gained this because of an odd response I gave during a conversation with my friends several years ago.
You see, I have this tendency to fade out during a conversation and stare blankly into the air if I don't have anything meaningful to say. I then snap back into reality and in a futile effort to rejoin the conversation, I repeat the last word I heard or thought I heard.
So this one time I snap back and mumble "huh... swan?", which was of course nothing like anything anyone had mentioned. Everyone thought this was so bizarre and/or humorous they decided to call me that for the rest of the day and they still do whenever I say something really weird or off topic.