c. 1300, "tumult, armed conflict, struggle with adversity or pain," from Anglo-French estur, Old French estour "a tumult, conflict, assault, shock, battle," from Proto-Germanic *sturmaz "storm" (source also of Old High German sturm "storm; battle;" see storm (n.)). Became obsolete, revived by Spenser and his followers in various senses; also surviving as a Scottish and Northern English word meaning "a (driving) storm" or "uproar, commotion." Italian stormo also is from Germanic.
