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.
adjective suffix, "full of or characterized by," from Old English -ig, from Proto-Germanic *-iga- (source also of Dutch, Danish, German -ig, Gothic -egs), from PIE -(i)ko-, adjectival suffix, cognate with elements in Greek -ikos, Latin -icus (see -ic). Originally added to nouns in Old English; used from 13c. with verbs, and by 15c. even with other adjectives (for example crispy).
<a href="https://www.etymonline.com/word/stormy">Etymology of stormy by etymonline</a>
Harper, D. (n.d.). Etymology of stormy. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/stormy