Most probably this represents an unknown/deleted user. Maybe this folder was cut and pasted from another place which had this user, but your current location doesn't have it. For deleted AD users it would usually show a SID instead of this, but Google search seems to prove this point that this is some missing user.
Then this is some missing user. If this folder didn't come from an outside, then this folder had a permission with a user, which is deleted in your domain. I sometimes saw this on our file server, although we tried to use groups instead of individual users for permissions as much as possible.
Well, this is some weird issue. Maybe you are using Terminal services/Remote desktop services and all user profiles are created on this server. But i can't say what could have caused such renaming of folders. I'm not 100% sure, but i think deleted group can also appear as a SID.