Is it ensure, insure, or assure?
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.