What does it mean to have Jiayu in the south?

Xiao Yanan's Journey to Yujia is a poem in the Book of Songs, the first collection of poems in ancient China. "There is Jiayu in the south, steamed cover, wine in the gentleman, and Yan Le Yi in the guest style." In the eleventh year of Baotai in the Southern Tang Dynasty (AD 953), the emperor passed through this place on a southern tour, tasted the fish paid tribute by local fishermen, and repeatedly praised: "Good fish, good fish!" Jiayu, thus named.