The word "髑髅" is formed by combining two characters, each structured as a phono-semantic compound. Both characters contain the semantic component "骨" (bone), indicating their relation to skeletal parts. The character "髑" incorporates "蜀" as a phonetic component to suggest pronunciation, while "髅" uses "娄" for the same purpose. Together, they create a disyllabic term specifically denoting "skull", with the semantic elements reinforcing the meaning and the phonetic elements guiding the sound.