Origins
The word 'order' demonstrates how a concrete, physical image — a row of objects arranged in sequence — can expand to govern the entire vocabulary of civilization, from military ranks to religious brotherhoods to the structure of the universe. It enters English in the thirteenth century from Old French 'ordre,' from Latin 'ōrdō' (genitive 'ōrdinis'), meaning a row, a line, a rank, a regular series.
The deeper etymology of Latin 'ōrdō' is uncertain. Some scholars connect it to PIE *h₂er- (to fit together, to join), which would make 'order' etymologically 'a fitting together,' but this is not universally accepted. What is clear is the word's semantic starting point: a row. Roman soldiers standing in battle formation were in 'ōrdō.' Threads arranged on a loom were in 'ōrdō.' Seeds planted in a line were in 'ōrdō.' From this physical image of sequential, regular arrangement, every subsequent meaning unfolded.
The Latin word generated an immense family of derivatives that permeate English. 'Ordinary' (from Latin 'ōrdinārius,' of the regular order or sequence) — something ordinary follows the expected pattern, the regular row. 'Extraordinary' (extrā + ōrdinārius, outside the regular order) — something extraordinary breaks the row, exceeds the sequence. 'Ordinal' (pertaining to position in a series — first, second, third). 'Ordain' (from Latin 'ōrdināre,' to put in order, to arrange) — originally 'to arrange,' then specifically 'to arrange someone into the priesthood.' 'Coordinate' (co- + ōrdināre, to arrange together). 'Subordinate' (sub- + ōrdināre, arranged below).
Development
The dual sense of 'order' as both 'arrangement' and 'command' reflects a real conceptual link: to command is to arrange. When a general gives an order, the purpose is to arrange soldiers into a desired formation — to impose an 'ōrdō' on the battlefield. When a customer places an order, they are arranging for goods to be delivered. The command sense derives naturally from the arrangement sense.
The religious sense — a monastic or knightly 'order' (the Benedictine Order, the Order of the Garter) — arose because these organizations were defined by their rule, their regulated way of life, their arrangement of daily activities according to a prescribed pattern. A religious order is a community organized by a shared ōrdō — a sequence of prayers, duties, and observances that structures every hour.
The German word 'Ordnung' (order, tidiness, regulation) was borrowed from Latin 'ōrdō' and has become one of the most culturally loaded words in the German language, often cited as encapsulating a cultural value. The phrase 'Ordnung muss sein' (there must be order) has no precise English equivalent in cultural weight. The Latin word that began as 'a row of soldiers' became, through its Germanic borrowing, a national ethos.