The word "狗腿" is formed by directly combining the character for "dog" (狗) with the character for "leg" (腿), creating a literal compound meaning "dog's leg". This structure follows a modifier-noun format where "狗" specifies the type of "腿". The term has developed a figurative usage, referring to a henchman or lackey, derived from the literal image of a dog's leg as a tool for servile action.