The best answer: In the Spring and Autumn Period, after Goujian paid tribute to Xi Shi, Qiongji, the daughter of Fu Cha, the king of Wu, lost her father’s love and drove Qiongji to the lake above the desert island to think over it. Later, when the Vietnamese army came to Gusu City, in order to save her life, Fu Cha prepared to give her daughter as a gift to Goujian to plead guilty and make peace, and Qiongji jumped into the lake and committed suicide. Later generations called this lake Joan Ji Lake in memory of Joan Ji. Because the pronunciation of Qiongji and Jinji in Wu dialect is similar, Qiongji Lake is gradually called Jinji Lake.
In the Spring and Autumn Period, Qiong Ji, the daughter of Fu Cha, the prince of Wu, lost her father’s love after Gou Jian paid tribute to Xi Shi. Fu Cha and Xi Shi are in Gusutai, Lingyan Mountain, west of Suzhou, enjoying themselves while ignoring politics. Joan Ji found Gou Jian had ulterior motives and asked her father several times to beware of Gou Jian. Fu Cha didn’t believe it, but listened to Xi Shi’s words and drove Qiong Ji to a desert island in the unnamed Great Lakes in the east of Suzhou to “think over the lake”. Later, when the Vietnamese army came to Gusu City, in order to save his life, Fu Cha prepared to give his daughter as a “gift” to Gou Jian to plead guilty and make peace. After hearing the news, Joan Ji jumped into the lake and killed herself. Legend has it that later generations called this lake “Joan Ji Lake” in memory of Joan Ji. Because the pronunciation of “Qiongji” and “Jinji” in Wu dialect is similar, “Qiongji Lake” is gradually called “Jinji Lake”.