When I was in the military people called me "Kirbs". This is a shorted version of my last name Kirby. It's normal in the military for people to be called by their last name. In the section where I worked a few coworkers would call out KIRBS! when I walked in... kinda like NORM on the show where "everybody knows your name" (yeah, you know the one).
When my wife had our third child I took a short leave and upon returning to work one of my buddies yelled out DADDYKIRBS! This kinda stuck and I adopted it as my online identity.
It's funny now that I've been using it for about 15 years online some people call me this in real life now too :)