French word arrondir comes from French rond, French a-, French -ir (A suffix forming infinitives of many verbs.)

Detailed word origin of arrondir

Dictionary entry	Language	Definition
rond	French (fra)	(colloquial) coin; (piece of) change, money. Circle (France, colloquial) drunk. Round (shape).
a-	French (fra)	A prefix forming words, especially verbs, that denote entering a state, making progress toward a goal, or the like. A-, non-, -less.
-ir	French (fra)	A suffix forming infinitives of many verbs.
arrondir	French (fra)	To round (make round).

Words with the same origin as arrondir