The word "stormwater" is a modern English compound, formed by directly combining two native Old English roots. "Storm" derives from the Proto-Germanic sturmaz, conveying a sense of tumult and disturbance, which is fitting for the intense, concentrated nature of the precipitation it describes. "Water" originates from the ubiquitous Proto-Indo-European root wod-or/wed-, meaning "water" or "wet." The compound's logic is transparently literal, naming the specific type of water generated by a storm event. Its contemporary usage is heavily shaped by environmental science and urban planning, where it denotes runoff that must be managed to prevent flooding and pollution.

Structure: storm (violent atmospheric disturbance) + water (liquid H₂O) - storm: From Old English storm, meaning "a violent disturbance of the atmosphere, a tempest." Its functional role is to specify the type or origin of the water. - water: From Old English wæter, meaning "water, a body of water." Its functional role is the core substance being described.