While we found no reference on the key of G-demolished, unofficial sources suggest that it's a musical pun against a "diminished" chord, which is a stack of thirds.
Other sources says that it was a quote delivered by Billy Gibbons on the season finale of "Bones" when his character (self) was asked for advice. When the person he said it to said, "I don't know what that means." Billy Gibbons replied- "You either know what it means or you don't."
The diminished chord is a triad with two minor thirds, or a minor third and a diminished fifth, which gives us an unstable chord, which needs to be resolved to another chord.
See a list of the best G guitar chords, suitable for beginners to advanced players at TheGuitarLesson.com.
Tip! Learn 10 Essential Principles for Learning Guitar at Tuts+.