The word "毛毛" is formed through the morphological process of reduplication, where the single character "毛" (meaning hair or fur) is repeated to create a disyllabic term. This repetition emphasizes the quality of being hairy, fuzzy, or covered in fine hairs, resulting in a word that typically refers to something like down, fuzz, or soft hair, often used in colloquial contexts for describing subtle textures or as a nickname.