The frog at the bottom of the well is derived from a fable in “Zhuangzi · Waipian·Qiu Shui”. The idioms “frog at the bottom of the well” and “seeing the sky at the well” are both derived from this fable and are used to metaphor and satirize the narrow-eyed and self-righteous people.
“Zhuangzi·Autumn Water” begins with a conversation between He Bo and Beihai. In autumn, the Yellow River is full of water, and the river suddenly widens, so wide that the cows and sheep on the opposite bank cannot be seen clearly. He Bo was so self-satisfied that he thought he was great, but when he came to the estuary and saw the sea, he knew how small he was. Beihai said: “Well frogs are not allowed to talk to the sea, they are stuck in the imaginary.”
This article later tells the complete story of the well frog. It is said that a frog lives in a trap and one day encounters a giant soft-shelled turtle from the East China Sea. The frog said to the turtle: “You see how happy I am. Go out and jump around the well. When you come back, you can rest in the hole in the well. In the water, you can just expose your head and mouth, and you can also step on your feet. In the soft mud. Which of those shrimps, crabs, and tadpoles can compare to me? I am the owner of this well, so happy! Why don’t you come to the well often to see?” So the giant turtle I want to get into the well, but the well is so small that I can’t even put my feet in it. The turtle said to the frog: “Have you seen the sea? Its width is more than a thousand miles? Its depth is more than a thousand miles? There were nine years of floods in the ten years of Yu Da Yu’s control of water, and it did not increase the amount of sea water. There have been seven years of drought, and the sea has not decreased much. The sea is so unaffected by floods and droughts, this is the great joy of living in the East China Sea.” The frog in the well heard it and was shocked, only to know where he was living. How insignificant the earth is.