"frozen rain, pellets of ice falling in showers," Old English hægl, hagol (Mercian hegel) "hail, hailstorm," also the name of the rune for H, from Proto-Germanic *haglaz (source also of Old Frisian heil, Old Saxon, Old High German hagal, Old Norse hagl, German Hagel "hail"), probably from PIE *kaghlo- "pebble" (source also of Greek kakhlex "round pebble").
Old English storm "violent disturbance of the atmosphere, tempest; onrush, attack, tumult; disturbance," from Proto-Germanic *sturmaz "storm" (source also of Old Norse stormr, Old Saxon, Middle Low German, Middle Dutch, Dutch storm, Old High German sturm, German Sturm), from PIE *stur-mo-, from root *(s)twer- (1) "to turn, whirl." Old French estour "onset, tumult," Italian stormo "a fight" are Germanic loan-words. Figurative (non-meteorological) sense was in late Old English.
Storm-wind is from 1798. Storm-door first recorded 1872; storm-water is from 1847; storm-window is attested from 1824. Storm surge attested from 1872. Adverbial phrase _______ up a storm is from 1946.