In a shallow well lived a frog. One day, a turtle from the Eastern Sea crawled onto the well's edge. The frog croaked boastfully, "I am so happy! I can hop along the railing, rest in the wall's crevices, swim leisurely in the water, or stand with mud just covering my feet. Look around—crabs, tadpoles—none are as joyful as I! I rule this entire well. Why don't you come see my wonderful home?"
The sea turtle nodded and began to enter, but before his left foot could move, his right knee got stuck on the well's rim, forcing him to carefully withdraw. He told the frog, "A thousand li cannot describe the ocean's breadth, nor a thousand zhang its depth. During Yu's reign, nine years of ten were floods, yet the sea never rose an inch. Under Tang, seven of eight years saw drought, yet the coast never receded a foot. Neither time nor calamity changes the sea—this is the greatest joy of the Eastern Ocean!"
The frog, stunned by these words, looked at the sea turtle with newfound humility and dared not croak again.
Later, the idiom "a frog at the bottom of a well" came to describe someone ignorant and narrow-minded.
Source: *Zhuangzi*, "Autumn Floods"
Meaning of the Idiom: Later, the Chinese idiom "井底之蛙" came to describe how someone ignorant and narrow-minded.