Fester

"Oh, no thanks. Not me. Think I'll just sit at home and Fester."
Kinda a sore loser name.

This is a name that my grandmother gave to her dog, because there was an annual festival in her town, and people who went were called "Festers". So, in that case it meant "dog who goes to the festival", hahah. But while I can see how this name works as a nickname for Silvester, I don't think it's a good idea for English-speakers because of its English meaning.

To Neko and Akito: yes, and yes. In English, that is what "fester" means. I'm already not a fan of Fester (or Silvester, for that matter), but the reference to rot is yet another reason why I would never use this name.
No matter how much I may love Uncle Fester. :-)