This is an interesting one if not a bit shameful.
I was making my first online gaming account ever and just typed in Chris, It was obviously taken but suggested LordChris, I typed in LordChris which was also taken (Suggetion Fail) but then suggested LordChris915. I used it ever since.
I then started looking up 915 on the internet to see if it meant anything, all I could find was a bible reference in Mark 9:15 whcih says "And immediately all the crowd, when they saw him, were greatly amazed and ran up to him and greeted him." I decided I would very much like to have a crowd amazed by me and come to greet me, so thats another reason why I kept it.
It also tickles my fancy as it makes me sound like an Aristocrat (Which I could claim very distantly to be) and fuels my delusions of grandeur.
Well there you go :)