Named after Hermann Regio - French astronomer of German origin, discoverer of asteroid (21) Lutetia (1802-1866).
A regio is a large area marked by reflectivity or color distinctions from adjacent areas, or a broad geographic region. On Lutetia they are named after discoverer of Lutetia, and provinces of the Roman Empire at the time of Lutetia.
Sorry, there hasn't been a good map made for this world yet :(