Let's see if I can remember everything there is.
Patchou was the creator of Messenger Live! Plus, a plug-in to Messenger Live that added a bunch of great features to it. I didn't want to steal his name, so I put a spin on it and made it into Patchisou. I remember trying so many different combination of letters and sounds, and that one fit the best.
Back then, Japanese oriented usernames that sounded like real names were the in thing around here, so I wanted to choose a last name. The first anime I ever watched knowing it was an anime was Fruits Baskets. Tohru Honda was the main character, so for my last name, I formed it around Tohru. I wanted a longer character string than Patchisou Tohru, so I added Yu to the front, because that's what sounded best from the long list of last names.
So in the end, I got Patchisou Yutohru. It's pronounced Patch-ee-sue You-toe-roo.