I know, because everybody is asking the same question. The book 'Freistunde' is even advertised with this promise: '
Darin wird auch ausführlich erklärt, wie Smudo zu dem Namen Smudo kam.'(in here it is explained how Smudo came to the name Smudo)!
See
http://www.elounge.de/f4/Shop/buch.htmHe also says somewhere that the alternative spelling S.M.U.D.O. that he used to use has no meaning whatsoever...
He's just playing with our minds :D