A quick lookup rendered this definition, "Not a cheese at all, but a sausage made from the meaty bits of the head of a calf or pig (sometimes a sheep or cow) that are seasoned, combined with a gelatinous meat broth and cooked in a mold. When cool, the sausage is unmolded and thinly sliced. It`s usually eaten at room temperature.".
At the first look I have known some people whose brains were as functional as this substance. Their proclivity to wearing a cheese hat is unknown although Mr Dean's picture is suggestive.
I doubt it. It would make a great Phd thesis though. Feingold could find a grant. Besides, not everyone considers it a pejorative.
No mystery/ no connection. It's the Cheese.