The compound "three-story" is a straightforward numerical descriptor in English architecture. Its first element, "three," descends from the ancient Proto-Indo-European numeral trei-, which is the common ancestor for numbers meaning "three" across many European and Asian languages. The second element, "story," has a more colorful journey. It originates from the Latin historia, meaning "history" or "narrative." In medieval Latin, historia was applied to a tier of windows or sculptures on a building facade that often told a story, such as from the Bible. This architectural term was borrowed into Middle English as "storie," which over time lost its direct association with narrative art and became the standard term for a building's floor. Thus, a "three-story" building literally denotes a structure with three such defined levels.

Structure: three (number) + story (level) - three: From Old English þrīe, þrēo, of Germanic origin; related to Dutch drie and German drei, from an Indo-European root shared by Latin tres and Greek treis. Functions as a numerical quantifier. - story: From Middle English storie, from Anglo-Latin historia (meaning a tier of painted windows or sculpture on a building), a specialized use of Latin historia (meaning history, tale). The architectural sense likely arose from the medieval practice of decorating different floors of a building with narrative paintings or sculptures. Functions as a noun denoting a floor or level of a building.