That one took me a while as well. I had to ask someone at work that knows street lingo. It's twofold apparently. G is like the hip, up to date thing, and it also represents the seventh block of the show which is also the seventh letter. Dumb I know.
Personally I'm getting a little tired of the rah-rah attitude on Fox. Along with the populist O'Reilly, Hannity has to be one of the most annoying people on the air. I only watch the morning show because it is a bit funnier and more relaxed than the other shows