The word "大叔" is formed by directly combining two meaningful characters: "大" (dà), meaning "big" or "elder", and "叔" (shū), which specifically means "father's younger brother" or "uncle". Together, they create a new, composite concept that moves beyond the literal, familial "younger uncle" to denote a middle-aged or older man, often with connotations of familiarity, respect, or a certain casual, everyday character. Its formation is a straightforward conceptual blend, using the familiar family term "叔" and modifying it with "大" to shift the meaning from a specific junior uncle to a general, non-familial category of older men.