The word "臃肿" is formed from two characters, each constructed as a phono-semantic compound. "臃" consists of the radical "月" (indicating relation to flesh or the body) paired with the phonetic component "雍" (suggesting its pronunciation), while "肿" similarly uses the radical "月" with the phonetic "中". When combined, the shared radical reinforces the word's association with physical form, resulting in a meaning that denotes swelling or bloating.