The word 'waterproofness' is a modern English formation built upon the established adjective 'waterproof.' The core concept originates from the Old English 'wæter,' a fundamental term for the liquid, combined with 'proof,' which entered English via Old French from Latin 'probare,' meaning to test. In the context of materials, 'proof' evolved to signify "impenetrable by" or "able to withstand" a specific element, as seen in terms like 'fireproof' or 'bulletproof.' The suffix '-ness,' of Germanic origin, is then appended to this adjective to create an abstract noun denoting the state or quality of being impervious to water. Thus, the term logically constructs the concept of a material's tested and proven resistance to water penetration into a named condition.

Structure: water (liquid) + proof (resistant) + ness (state/quality) water: Old English origin, referring to the clear, colorless liquid. In this compound, it specifies the substance being resisted. proof: From Middle English, ultimately from Latin probare (to test or prove). In compounds, it means "resistant to" or "impervious to." ness: An Old English noun-forming suffix used to create abstract nouns indicating a state, condition, or quality.