The word "身材" is formed by combining the character "身", which means "body", with "材", which means "material" or "inherent quality". Together, they create a compound where "身" provides the core concept of the physical self, while "材" adds the notion of form or composition, resulting in a literal sense of "body material" that metaphorically conveys one's physical figure or stature. This fusion exemplifies how Chinese often constructs terms by semantically linking individual characters to express a unified, nuanced idea.