The word 'water-ski' is a transparent 20th-century compound formed by combining two pre-existing nouns. The first element, 'water', has ancient Proto-Germanic roots, ultimately from the Proto-Indo-European wódr̥, referring to the essential liquid. The second element, 'ski', entered English from Norwegian, tracing back to the Old Norse 'skíð' for a billet of wood or snowshoe. The compound's logic is perfectly literal: it describes the activity of using a 'ski'—a device originally for snow—on the surface of 'water', innovatively adapting the principle of gliding to a new medium. It exemplifies how English readily creates new terms by directly combining familiar words to describe novel inventions and sports.

Structure: water (liquid) + ski (snow runner) water: From Old English 'wæter', of Proto-Germanic origin; related to Dutch 'water' and German 'Wasser'. Functions as a noun denoting the liquid medium in this compound. ski: From Norwegian, from Old Norse 'skíð' meaning "stick of wood, snowshoe". Functions as a noun denoting the equipment used for gliding.