Clearly, you are all mistaken.

I have it on the highest authority that the "G" stands for none other than Gilderoy Lockheart.

You may recall he was rather famous for his memory charms... Even if the "G" had stood for anything other than this previously, you would never remember...

He's been in the special effects department since forever. He worked on Black Beast. There's not a single beast in there—but you think there is. He's that good.