The compound noun "water-supply" is a transparent combination of two fundamental English words. "Water" descends from the Proto-Indo-European root wódr̥, a term for the essential liquid, which evolved directly into the Old English 'wæter'. "Supply" originates from the Latin verb 'supplere', meaning 'to fill up', which entered English via Old French, carrying the sense of providing what is needed. The logic of the compound is perfectly literal: it names the system or act of filling up the need for water. From these concrete roots—one naming the elemental substance and the other the act of fulfilling a requirement—the term evolved to describe the complex, modern infrastructure and services essential for urban and agricultural life.

Structure: water (liquid) + supply (provision) water: Origin: Old English 'wæter', from Proto-Germanic watōr, from Proto-Indo-European wódr̥. Functional role: The core noun, specifying the substance being provided. supply: Origin: Middle English 'supplien', from Old French 'souploier', from Latin 'supplere' meaning 'to fill up, complete'. Functional role: The noun derived from the verb, indicating the action or system of providing.