The word 老弟 is formed by combining the familiar and affectionate prefix 老 (lǎo), which here implies a sense of seasoned closeness rather than age, with 弟 (dì), meaning "younger brother". This fusion creates a single term of address that conceptually frames the addressed person within a relationship of informal kinship and friendly camaraderie, as if they were a younger brother within an extended familial or social circle. The term is not literal but culturally metaphorical, building a bond of assumed familiarity and affectionate regard through this conceptual blend.