Why is the ninth month called September?
early 14c., from Old French diocese (13c., Modern French diocèse), from Late Latin diocesis "a governor's jurisdiction," later, "a bishop's jurisdiction," from Greek dioikesis "government, administration; province," originally "economy, housekeeping," from dioikein "control, govern, administer, manage a house," from dia- "thoroughly" (see dia-) + oikos "house" (see villa).
in some Christian churches, a territorial area administered by a bishop. The word originally referred to a governmental area in the Roman Empire, governed by an imperial vicar. The secular diocese was subdivided into provinces, each with its own governor; but, in the ecclesiastical adaptation of the system, the province became the larger territorial unit, administered by a metropolitan bishop and subdivided into dioceses.