Tao Yuanming, a renowned writer of the Eastern Jin Dynasty (317-420), authored the famous essay Peach-Blossom Spring. It narrates the tale of a fisherman who accidentally discovers a hidden land of the same name. After squeezing through a narrow cave, he finds a village inhabited by descendants of refugees from the Qin Dynasty. This place is a paradise isolated from the outside world, free from exploitation and oppression, where everyone lives and works in peace and contentment. After leaving, the fisherman could never find his way back to this idyllic world.
This idiom, derived from the story, refers to an isolated, ideal world or utopia.