A few notes...this is my first post to the list, and this discussion is what drew me forth.

The midwest DJ's name you're looking for is Alan Freed. Freed was a DJ in Cleveland who gathered a great following by promoting rock 'n' roll music, and then went to New York to be ruined by the payola scandal. I think that it's a good guess that the expression has sexual connotations, no?

As for "jazz," from what I've read, its origins are a bit murkier. I've heard that the word was originally spelled "jass," or "jas." I've heard that the word has roots in African language, and that it originally was uttered in reference to sex. I don't think etymologists have a true conclusion on this one.