Etymology: < Anglo-Norman -orie and Old French (early and regional) -orie (Old French, Middle French, French -oire ) < classical Latin -ōria (as in e.g. glory n., victory n.), although corresponding also in many cases to classical Latin -ōrium (as in e.g. oratory n.¹, purgatory n.).On the analogy of early borrowings from Anglo-Norman, -ory came to be the normal English representation of classical Latin -ōria , -ōrium , French -oire . The most numerous of these are adaptations of classical Latin neuter nouns in -ōrium , from adjectives in -ōrius (see -ory suffix²), or formations of the same type. A few reflect Latin agent nouns in -or with the ending -ia -y suffix³, e.g. curatory n. The earliest examples date from Middle English, e.g. purgatory n. (13th cent.), oratory n.¹ (14th cent.), dormitory n. (15th cent.); borrowings continue to be numerous down to about 1700, e.g. oratory n.² (16th cent.), reservatory n. (17th cent.), but (like the latter) the majority are rare or obsolete. Since 1700 few such words have appeared. English formations, chiefly on the past participial stem of Latin verbs or the English verb stems derived from them, are found from around 1500, e.g. masticatory n., reportory n. (16th cent.), manufactory n., observatory n. (17th cent.), expectoratory n. (19th cent.), Vanitory n. (20th cent.). Some nouns with this element have doublets (generally more frequently used) in which the Latin form in -orium is retained, e.g. auditory n., crematory n. besides the more frequent auditorium n., crematorium n.: see -orium suffix. The endings of some words in -tary , -ter(r)e , -tre , etc., were assimilated to this termination in the 15th and 16th centuries, e.g. fumitory n., pellitory n.¹ As it occurs in noun formations, the initial vowel of -ory is in British English reduced or elided, giving a pronunciation of /(ə)ri/.

Etymology: < Anglo-Norman -orie (Old French, Middle French, French -oire ) < classical Latin -ōrius , -ōria , -ōrium < -or , suffix forming nouns (see -or suffix) + -ius , suffix forming adjectives (compare sorōr sister, sorōrius sisterly). Classical Latin adjectives of this type are chiefly formed from agent-nouns in -tor , -sor , but sometimes apparently from the corresponding past participial stem in -t- , -s- ; examples include accūsātōrius accusatory adj., suāsōrius suasory adj., dēcrētōrius decretory adj.Loanwords from Latin (sometimes via French) with this terminal element are first attested from the Middle English period to around 1700, e.g. accusatory adj. (14th cent.), peremptory adj. (15th cent.), desultory adj. (16th cent.), contradictory adj. (17th cent.); they reach a peak in the 17th cent., after which relatively few are introduced. Formations in English on the Latin past participial stem in -t- or -s- , especially when inferrable from an agent noun in -or , appear to date from the 15th cent. and to become increasingly common, e.g. contributory adj. (15th cent.), applicatory adj. (16th cent.), malefactory adj. (17th cent.), spoliatory adj. (18th cent.), conclusory adj., modificatory adj. (19th cent.). Not always distinguishable from these are formations on English first elements (chiefly verbs of Latin origin, and especially those ending in -ate ), in which the termination has remained productive, e.g. advisory adj., statutory adj. (18th cent.), alleviatory adj., supervisory adj. (19th cent.), celebratory adj., repressory adj. (20th cent.). Adjectives in -ory not infrequently have parallel formations (usually less common) in -ive suffix, e.g. defensory adj. besides defensive adj., punitory adj. besides punitive adj.; but compare derisory adj. and derisive adj. Instead of -ory , the English adjective has often the extended form -orial suffix, less frequently -orious suffix. As it occurs in adjectival formations, the initial vowel of -ory is in British English reduced or elided, giving a pronunciation of /(ə)ri/.