As I first joined a counterstrike clan I had to think of a name. The clan was "KNIGHTS" and everyone had a name like "HolyKnight", "WhiteKnight", "HornyKnight" and so on ... I've chosen "BlackKnight".
After I left the clan I liked the "Black" part so much (favorite color too) that I stuck with it .. but I had to add something because the name "black" is taken on almost every site, board,.. So I added a "666" because 6 is my favorite number and "666" gives the "black" an evil touch. So "black666" was born and I used it ever since.