What is summer on the unnamed lake?

Summer by the unnamed lake is a network language, which originated from the TV series Princess Zhu Huan. Xia was the lover of Emperor Qianlong when he was young. She met Emperor Qianlong in Daming Lake and gave birth to his future Xia Ziwei. This stalk is used to describe people or things that make people feel deja vu in certain scenes and situations, just like old friends.