'arrondissement' originates from French, specifically the word 'arrondissement', where 'arrondir' (with the prefix 'a-' from Latin ad-) meant 'to make round' and the suffix '-ment' formed a noun meaning 'the act or result'.

'arrondissement' developed in French from the verb 'arrondir' (to make round), which in turn comes from Old French elements related to 'rond' (round) ultimately from Latin 'rotundus'; the noun formation with '-ment' produced 'arrondissement' and the term entered English usage borrowing the French form.

Initially, it meant 'the act or result of making round' (a rounding), but over time it evolved into the administrative sense of 'a defined territorial district' used in modern French and English.