Since the buzztime forums fell into a black hole, I guess we have to rehash the stories here
The story of POMAN goes back to my summer job in my college days.
Back then, the Pittsburgh Pirates were actually relevant (in the midst of 3 consecutive division titles
). One of their star players was Bobby Bonilla, who was called "Bobby Bo" by the media/fans, for short.
Since my first name is Rob and the first two initials of my last name are Po....co-workers started calling me "Robby Po" as spinoff of "Bobby Bo." Eventually the "Robby" dropped off and they just started calling me "Po." And shortly after that, they decided "Po" was too short and they started calling me "Poman." That's where the nickname stuck