During the Warring States period (475-221 BC), there lived a renowned archer named Geng Ying, whose skill was unmatched in his time.
One day, while standing beside the King of Wei, a flock of swan geese flew overhead. Confidently, Geng Ying said to the king, "The mere twang of my bowstring could bring down a bird." The king was skeptical.
Just then, a solitary swan goose appeared, flying low and slow, its cry sad and dolorous. Instantly, Geng Ying bent his bow and pulled the string forcefully. Twang! The shrill sound soared into the air, and down fell the bird to the ground. The king watched in bewilderment.
Geng Ying then explained: "The bird was flying low and slow because it was already injured. It cried bitterly because it had lost its companions. Being hurt and heartbroken, the twang of my strong bow—a sound birds dread most—startled it. The shrill sound made its heart race, its wings weaken, and its balance falter. Thus it fell, much like a man dropping his chopsticks at a sudden clap of thunder during a meal."
Hence comes the idiom "a bird startled by the mere twang of a bowstring," illustrating how someone who has been repeatedly frightened in the past can become numb and paralyzed when faced with a new, similar threat, unsure how to respond.