I wrote The Pool sometime in mid-2001. My memory has always been that I just hammered it out one night in a couple of hours. And that's true, in terms of the writing of the actual document. But I must have been thinking about the idea for a while prior to that.
Here's a pic of a note I had in an old sketchbook. The entry just before this was dated 06-19-01 and this entry seems to suggest that I hadn't actually written the game yet, but I clearly had most of the mechanics in my head.
What's most interesting to me is that bit about the GM having a secret pool of dice you can gamble from "in the dark". That isn't part of the game so it must be something I briefly considered and then dropped. I wonder how the game would play with that bit included?