Ha, yes, it is indeed from Buffy. My first forays online back in the infancy of the internet was on Buffy forums and chat. I just kind of stuck with it. Some places I have a williamthebloody handle, and others it's BloodyWilliam.
Same! "The internet" to me was just the Buffyverse for a good long while. My [oh-so-very-clever] username was "ilovebuffy." (lol, so lame in retrospect.)