I forgot my belt and have a sizeable layover at ATL, is there somewhere I could buy a belt? None of the retail outlets have names I recognize as selling clothing or at least accessories.
You can certainly buy a belt airside at ATL.
Hartsfield-Jackson's website offers a directory of retail concessions, which includes pictures of most of the storefronts— you need not be familiar with the names; you can scroll through and find something that doesn't sound like a newsstand or electronics store and see from the picture or read from the blurb. For instance, the intro for Brighton mentions that it started out as a retailer for belts (I'm not sure if it is for men or women or both).
You will probably not find any deals, as the stores make their rent by charging "convenience prices" for travelers, and the clothing stores seem to be mostly upper-middle market. But there is probably at least one shop in each concourse with some kind of belt available, e.g. Zegna on Concourse A, Sean John on B, Johnston & Murphy on D, Brooks Brothers on E and in the Atrium, and Tommy Hilfiger on F.