mid 17th century: from proprietary, on the pattern of pairs such as depositary, depositor. Proprietary is late Middle English (as a noun denoting a member of a religious order who held property), from late Latin proprietarius ‘proprietor’, from proprietas (see property)
17世紀中頃。proprietary から。depositary / depositor のような対にならったもの。proprietary は中英語後期(財産を持つ修道会の会員を表す名詞として)で、後期ラテン語 proprietarius「所有者」に由来し、proprietas から成る(property を参照)。