"Yan" refers to Yan Zhenqing and "Liu" refers to Liu Gongquan. They are all four famous regular script writers in the ancient calligraphy history of China: Yan Zhenqing's calligraphy is clumsy and appears healthy and free and easy. Liu Gongquan's calligraphy has sharp edges and corners, and is famous for strengthening bones. "Yan Gu" means that their style is as strong as bones and muscles. Yan Liujin is from Song Fan Zhongyan's Bachelor of Sacrificing Stones: "Man Qing's pen, Yan Liujin." Yan Liu's and Yan Liu's calligraphy are both powerful, but their styles are different. Also known as excellent calligraphy.
The Tang Dynasty was the heyday of calligraphy. When it comes to regular script, the characters must be called Yan and Liu. China's regular script reached its peak in the Tang Dynasty, with Yan Zhenqing as its representative. Liu Gongquan, a calligrapher later in the Tang Dynasty, was also influenced by Yan Zhenqing, and was later called Yan Liu.
Yan Zhenqing's calligraphy is full of strength and style; Liu Gongquan's calligraphy emphasizes strength and strength, so it is also called "Yan Gu".