"a roundabout or circuitous way," 1738, from French détour, from Old French destor "side road, byway; evasion, excuse," from destorner "turn aside," from des- "aside" (see dis-) + tourner "to turn" (see turn (v.)). In 18c. usually figurative. Usually treated as a French word in English (with italics and the accent mark) until late 19c.
1835, "make a detour" (intransitive); 1897, "send on a detour" (transitive), from detour (n.). Related: Detoured; detouring.