Etymology: < classical Latin -ōri- (in -ōrius , -ōria , -ōrium : see -ory suffix1, -ory suffix2) + classical Latin -ālis -al suffix1.The termination originally arose in English words derived (in some cases probably via French) from Latin words ending in -ōriālis formed from nouns in -ōrium , -ōrius (see -ory suffix1) by the addition of -ālis (see -al suffix1), e.g. consistorial adj., victorial adj. (15th cent.), executorial adj., territorial adj. and n. (18th cent.). It extended its scope in English to derivatives in -al suffix1 of Latin adjectives in -tōrius , -sōrius , e.g. oratorial adj.1, possessorial adj., purgatorial adj. (16th cent.), mediatorial adj., pictorial adj. (17th cent.), dictatorial adj. (18th cent.), sartorial adj. (19th cent.). Since many of these Latin adjectives are themselves derivatives of agent nouns, the pattern became established of adding -ial suffix to Latin and English agent nouns in -tor and -sor , e.g. ancestorial adj., rectorial adj. (17th cent.), editorial adj., electorial adj., equatorial adj. (18th cent.), moderatorial adj. (19th cent.) and hence to other nouns of generally similar form and meaning, e.g. ambassadorial adj. (18th cent.), monsignorial adj. (19th cent.), so that -orial is felt to be the adjectival ending corresponding to nouns in -or ; compare also newspaporial n. and adj. (18th cent.), reportorial adj. (19th cent.). A few English formations in -orial on words derived from the past participial stem of Latin verbs occur, e.g. reductorial adj. (18th cent.) and perhaps migratorial adj. (19th cent.). In sense, these adjectives in -orial are usually identical with those in -ory (see -ory suffix2), and the two forms are not rarely found side by side (e.g. piscatorial adj., piscatory adj.); but -orial is preferred for the adjective when there is a noun in -ory (see -ory suffix1) (e.g. purgatory n., purgatorial adj.). Words in -orial from agent-nouns are chiefly of English formation, the compound suffix being rare in French.
This entry has been updated (OED Third Edition, September 2004; most recently modified version published online September 2019).