“Maru” of “Marunouchi” means circle (〇) in Japanese, “Otemachi” also has a circle (〇) as an initial letter in it’s name.
OAZO, is a name that express “Office & Amenity Zone (=AZ),” between these two (O) areas comprehensively.
Furthermore, “OAZO” means “oasis” in Esperanto.