mumbly Joe

noun1

1. •
   (slang, humorous) Someone who mumbles and is difficult to understand when speaking.

   • "Except, um... there's this election next week, so after that, it might not be him anymore. It might be what's-his-name, uh... Mumbly Joe, uh... I saw him on TV the other... uh... Bob Dole!" — 1996