Used to be TheGrimReaper on another site, that got shortened to Grim Reaper, which finally became Grim.
Pepe Le Quagmire on the other hand is a joke name.
Why people call me Barry is another story, I used to be Bobby Barrows on another site (Bobby is a serial killer in the fictional Clock Tower video game series known as the Scissorman), people just started calling me Barry for short so that was what my username became over there.