The word 老兄 is formed by combining the character 老 (lǎo), which here conveys a sense of familiarity and informal respect, with 兄 (xiōng), which means "elder brother". Together, they create a term of direct address that metaphorically extends the concept of "brother" and adds the affectionate, seasoned nuance of "old" to express camaraderie and friendly regard between men, similar to the English "old chap" or "buddy".