Inner component nested inside the
衣 wrapper, supplying the sound (gōng → gǔn, a regular tone-and-final shift inside the same labial-velar family). Carries a quiet semantic echo too: the robe was worn by the emperor and the
三公 (Three Dukes), so a 'ducal/public garment' is a passable mnemonic gloss. Same phonetic-and-semantic doubling appears in
滚 (roll) and
衮's variant
袞.