In the Warring States Period, there was a man in the State of Wei called Geng Lei. One day he said to the king: 'I can shoot down birds by simply plucking my bowstring.' When the king expressed doubt, Geng Lei pointed his bow at a wild goose flying in the sky, twanged the bowstring, and the goose fell to the ground. Geng Lei said, 'This goose has been hurt in the past. Hearing the twang of the bowstring, it assumed that it was doomed. So it simply gave up trying to live.
戰(zhàn)國時期（公元前403―221年中國中原地區(qū)各諸侯國連年爭戰(zhàn)的時代）魏國有個名叫更羸的人。一天，他對國王說：“我只要拉開弓，空射一下，就能把天上的鳥射下來?！眹醪幌嘈拧８銓侍焐巷w來的一只雁射去，果真那只雁聽到拉弦的聲音就掉了下來。國王感到很奇怪。更羸說，“那是一只受過傷的雁。它一聽到我拉開弓弦的聲響，就驚慌得支持不住，自然要掉下來了?！?/div>

This idiom means that if one has been frightened in the past one's will may become paralysed in a similar situation.
“驚弓之鳥”這個成語比喻受過驚恐之后，有一點動靜就特別害怕。