Literally DOWNtown - as in under the town.
By the way, in this article, the Journal Record calls it the "'Tunnel System' - formerly referred to as the Conncourse." I like this much better. The Conncourse says nothing as to what it is. Saying, "Yeah, it's in the tunnel system, just go to the X entrance," makes more sense to me. Also, if you can, you should pick up a copy of The Journal Record today, or sign-up online for their one-day free pass. It's crammed with good articles about Uptown, the Tower Theater plans, a nice article on the Redhawks' announcer Jim Byers and a lot more. Great edition today!
From the Journal Record:

They're doing a great job lately at The Journal Record !

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