Толковый словарь английского языка Oxford English Reference - ory

1. suffix forming nouns denoting a place for a particular function (dormitory; refectory). Derivatives -orial suffix forming adjectives. Etymology: L -oria, -orium, sometimes via ONF and AF -orie, OF -oire 2. suffix forming adjectives (and occasionally nouns) relating to or involving a verbal action (accessory; compulsory; directory). Etymology: L -orius, sometimes via AF -ori(e), OF -oir(e)