Round about the time we ordinary mortals were getting our first access to the Internet, we'd befriended another group of folks in my local and it turns out they gave nicknames to everyone and mine was Emperor. It stuck (there are people I know from the boozer who don't know my given name. Back in the day if you'd gone into my local and asked for The Emperor someone would have pointed you in the right direction) and is now, for all effects and purposes, my Common Law name. So it made sense to use that name when I had to create a username online and I've not felt the need to change it since.