An Etymological Dictionary of Astronomy and Astrophysics

An atmospheric disturbance with strong winds accompanied by rain, snow, or other precipitation and often by thunder and lightning.
A violent disturbance or upheaval.

Etymology (EN): M.E, from O.E. storm; cf. O.S., M.L.G., M.Du., Du. storm, O.H.G., Ger. sturm.

Etymology (PE): Tufân “storm; the roaring of the sea; noise, confused hum of men or animals,” Lori tufo, Laki tuf “intense shower accompanied by wind,” from tufidan “to roar, raise a tumult.”