The word 屋子 is formed by combining the character 屋 (wū), which originally depicted a pictograph of a house or room with a sloping roof and walls, representing the core concept of an enclosed shelter, with the character 子 (zi), a very common and ancient suffix that, when attached to nouns, often adds a sense of familiarity, diminutiveness, or concreteness. In this fusion, 子 transforms the more formal or architectural idea of 屋 into a more commonplace, everyday term for a room or a house, creating a single, integrated concept that feels more intimate and tangible than the root character alone.