Metaphysical meaning of Millo (mbd)
Millo, mil'-lo (Heb.)--filling up; making full; fullness; abundant; mound, i. e., filled with earth or stones; rampart; fortress; castle.
In Judges 9:6, 20 the fortress in or near Shechem is meant. In II Samuel 5:9 Millo is in the "city of David," or Jerusalem; it must therefore refer to a fortified part of the city of Jerusalem, or a fortification very near the city.