Surname Overview
The surname Mu is pronounced mù and is relatively uncommon today. It is found in Beijing, Songjiang in Shanghai, Qiubei in Yunnan, Nenjiang in Heilongjiang, Changli in Hebei, and Taiyuan, Xinzhou, and Yanbei in Shanxi; it occurs among the Han, Manchu, Hui, and Yi peoples.
Reference: 沐姓_沐姓的来源和历史_百家姓
Origins
Reduction from Duanmu
The surname Mu is often said to have been simplified from Duanmu. Mu Chong, a Han-dynasty governor of Dongping, stated that his ancestors originally bore the surname Duanmu and shortened it to Mu to avoid an enemy.
Reference: 沐姓起源分布与家谱家族
The Mu River Origin
Another explanation identifies Mu as the name of a river in Qingzhou and suggests that the surname arose from that place-name; it also associates the surname with the commandery of Hejian.
Reference: 沐姓_沐姓的来源和历史_百家姓
Commanderies and Clan Halls
Commandery Seats
The recorded commandery seats of the Mu surname are Hejian and Dongping.
Reference: 沐姓_沐姓的来源和历史_百家姓
Migration and Distribution
Migration in Yunnan
At the end of the Ming dynasty, some members of the Mu clan fled to Dacun in Hexi Town, Tonghai, which is described as a major source of the Mu surname in present-day Yunnan. Later, clan members moved to various places in Tonghai and expanded into Yuxi, Honghe, Dali, Qujing, Baoshan, Chuxiong, Zhaotong, and Kunming.
Reference: 云南沐姓溯源:沐英后裔的血脉传承与历史脉络-趣历史网