Hai Collection, Upper Volume Radical: Bone (gǔ) 髑 Kangxi strokes: 23 Page 1450, Entry 57 Pronounced du According to the Explaining Graphs and Analyzing Characters (Shuowen Jiezi), it refers to the skull or the nape of the neck. See the entry for the character lou for detailed notes. According to the Broad Rhymes (Guangyun), it is the same.