Kongero means cluster, congro means something like borough, neighborhood, or group. The congro started as clusters of koro and pseudo-wahi, being the work areas, but eventually they built more and it all clumped together, save for up near Bo-congro and Le-congro. Su-congro and Po-congro are actually in the middle of that, because it has the wastes as a wahi, and the various koro clumped around the waste yard/melting ground and pit ruins respectively.