大哥 (dà gē) literally combines 大 (dà, 'big' or 'eldest') and 哥 (gē, 'older brother'), forming a term that primarily means 'eldest brother' in a family context. It emphasizes birth order and carries connotations of seniority, responsibility, and respect within the sibling hierarchy.

Beyond blood relations, 大哥 is widely used as an honorific for any older male peer—such as a senior colleague, a mentor, or even a friendly older acquaintance—to convey warmth and deference. Unlike formal titles like 先生 (xiānsheng), it feels more approachable and familial. In some regional dialects or informal groups, it may even be adopted playfully among peers regardless of actual age, though this depends heavily on context and relationship closeness.