'archdiocese' originates from Late Latin, specifically the word 'archidioecesis', where the prefix 'archi-' meant 'chief' and 'dioecesis' meant 'administration' or 'district'.

'archdiocese' changed from the Late Latin 'archidioecesis' (formed from Greek elements) into Middle Latin and then entered English via Medieval ecclesiastical usage, eventually becoming the modern English word 'archdiocese'.

Initially it referred broadly to a chief administration or district; over time it came to mean specifically the district under an archbishop ('archdiocese').