'archdiocesan' originates from a combination of the prefix 'arch(i)-' from Greek and 'diocesan' from Late Latin/Greek, where 'arch(i)-' meant 'chief' or 'principal' and 'dioikesis' (Greek) meant 'administration' or 'management'.

'archdiocesan' developed from the noun 'archdiocese' + the adjectival suffix '-an'. 'Archdiocese' itself comes from Greek 'archi-' + 'dioikesis' via Latin 'archidioecesis' and Medieval Latin forms, eventually entering English as 'archdiocese' and then forming 'archdiocesan'.

Initially it combined the sense of 'chief' + 'administration' (i.e., the principal administrative district of the church); over time it has come to mean specifically 'relating to an archdiocese' or 'a person belonging to an archdiocese'.