People in eastern Sichuan and northern Fujian have many similar customs and habits. What is the origin between them?

There are two origins: First, northern Fujian belongs to Hakka area. During the second and third southward migration of Central Plains people, a large number of northerners fled to this area, including Sichuanese. Second, the population migration policy of "Jiangxi fills Huguang and Huguang fills Sichuan" was implemented in Qing Dynasty. A large number of Fujian people moved to Sichuan thousands of miles away, forming today's Hakka people in eastern Sichuan and retaining a large number of Hakka customs in northern Fujian.