A bird startled by the sound of a bowstring
During the time of the Warring States (475-221 BC), there lived a well-known archer named Geng Ying whose art in shooting was excelled by none at his time.
One day, as he was standing by the King of Wei, a flock of swan geese were flying over. With confidence, Geng Ying said to the king, "Just the twang of my bowstring can bring down a bird." The king greatly doubted him, until a solitary swan goose appeared, low and slow in its flight, sad and dolorous in its cry. Geng Ying bent his bow and plucked the bowstring. Twang! The shrill sound went high into the air and down fell the bird to the ground. The king was awed by this feat. Geng Ying then explained: "The bird was flying low and slow, because it was already hurt; it was crying in a bitter tone, because it had lost its companions. Due to the fact that it was already hurt and sad at heart, the twang of my strong bow, what the bird dreaded most, startled it. The shrilling sound made its heart beat fast, its wings weak, its balance uneven. Thus it fell down just as commonly as a man drops his chopsticks, when thunder strikes at the dinner table."
Henceforth comes the idiom "A bird startled by the mere sound of a plucked bowstring," illustrating a case where a man who had been previously and repeatedly frightened became numb and stupefied by a new thing of the same nature not knowing how to face the new situation.