Why are the names of The Eight Parts of Demi-Gods non-mainstream?

First of all, not all the names in Tianlong Babu are non-mainstream, some names are very normal. Secondly, why are some names so uncommon? Because the background of the novel is the Northern Song Dynasty, among the various ethnic groups in the north. story, so some surnames are from other ethnic groups, so they look non-mainstream. Below are all the main characters. Duan Yu, Mu Wanqing, Zhong Ling, Xiaolei, Duan Zhengming, Duan Zhengchun, Duan Yanqing, Dao Baifeng, Qin Hongmian, Gan Baobao, Ruan Xingzhu, Mrs. Wang, Wang Yuyan, Gao Shengtai, Batianshi, Hua Hegen, Fan Hua, Chu Wanli, Gu Ducheng, Fu Sigui, Zhu Danchen, Nanhai Crocodile God, Yun Zhonghe, Zhong Wanchou, Cui Baiquan, Guo Yanzhi, Master Kurong, Original Cause, Original View, Original Phase, Original Shen, Master Huangmei, Po Yu, Po Ai, Jiumozhi, Xiao Feng, Xiao Yuanshan, A'Zhu, A Zi, You Tanzhi, Kang Min, Bai Shijing, Chen Guyan, Wu Changfeng, Quan Guanqing, Zhang Quanxiang, Li Chunlai, Liu Zhuzhuang, Yi Dabiao, Wanyan Aguda, Yelu Hongji, Yelu Chongyuan, Yelu Nerugu, Helibu, Yelumoge, Shili, Polasu, Youji, Youju, Zhao Qiansun, Shanzheng, Shanboshan, Shanzhongshan, Shan Shushan, Shan Jishan, Shan Xiaoshan, Master Zhiguang, Pu Zhe, Xiang Wanghai, Qi Liu, Bao Qianling, Xu Zhuocheng, Tan Gong, Tan Po, Tan Qing, Xu Zhu, Xuan Ci, Ye Erniang, Wu Ya Zi, Tianshan Tongmao, Li Qiushui, Li Qinglu, Su Xinghe, Ding Chunqiu, Kang Guangling, Fan Bailing, Gou Du, Wu Lingjun, Xue Muhua, Feng Asan, Shi Qinglu, Li Puppet, Zhaixingzi, Tianlangzi, Chuchenzi, Wu Laoda, Sang Tugong, Xuanhuangzi, Zhang Dafu.