WoWInterface - Get Zone Layer Names from Map Dropdown

When you have the map open to a zone like, say, Oribos, there's a drop-down in the upper left corner that lets you select the maps for different floors. Each of these floors is named. For example, if you look at the map for Oribos, you see "Ring of Fates", "The Broker's Den", "Ring of Transference", and "The Crucible".

I've spent about an hour looking at fstack then digging through the WoW interface code trying to figure out where these strings actually come from, and I can't for the life of me seem to figure it out.

I'm hoping that there's some way that, given a map ID, I can return the list of the strings in those dropdowns (presumably, the same way that the dropdowns themselves get the strings). So, given an Oribos map ID like 1670, I could return {"Ring of Fates", "The Broker's Den", "Ring of Transference", "The Crucible"}

C_Map.GetChildInfo on the parent map gets me the map IDs of the maps corresponding to each layer, but I can't figure out where those names for the different layers that you see in the dropdown are coming from - the only names I can seem to find associated with them all just say "Oribos", not "Ring of Transference", etc.