also archi-, word-forming element meaning "chief, principal; extreme, ultra; early, primitive," from Latinized form of Greek arkh-, arkhi- "first, chief, primeval," combining form of arkhos "a chief, leader, commander," arkhein "be first, begin" (see archon).
"district and population under the pastoral care of a bishop," mid-14c., from Old French diocese (13c., Modern French diocèse), from Late Latin diocesis, in the Roman Empire "a governor's jurisdiction, a subdivision of a prefecture containing a number of provinces," later, in Church Latin, "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" (from PIE root *weik- (1) "clan").
<a href="https://www.etymonline.com/word/archdiocese">Etymology of archdiocese by etymonline</a>
Harper, D. (n.d.). Etymology of archdiocese. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/archdiocese