Английский Этимологический словарь - stir (v.)

- O.E. styrian, from P.Gmc. *sturjanan. The noun sense of "commotion, disturbance, tumult" (c.1375) is probably from O.N. styrr "disturbance, tumult" (see storm), from the same P.Gmc. root; the sense of "movement, bustle" is probably from the Eng. verb.