Английский Этимологический словарь - order (n.)

- 12c., from O.Fr. ordre, from earlier ordene, from L. ordinem (nom. ordo) "row, rank, series, arrangement." Earliest Eng. sense was ecclesiastical (holy orders, etc.); meaning "command, directive" is first recorded 1548, from the notion of "to keep in order." Phrase in order to preserves etymological notion of "sequence." The word reflects a very medieval notion: "a system of parts subject to certain uniform, established ranks or proportions," and was used of everything from architecture to angels. The verb is c.1200, from the noun. Orderly (adv.) is 15c.; as a noun meaning "military attendant who carries orders" it is first attested 1800.