Why gribbly?
In 1997, id Software released Quake II, and I played a bunch of it. I was bad at it, but had a lot of fun!
Of course, to play Quake II you needed a "handle", a screen name. I picked one based on a formative game from my Commodore 64 childhood - Andrew Braybrook's 1985 gem "Gribbly's Day Out":

You can play it here on archive.org!
It was around then that I registered gribbly.org, and have (under) used it ever since!