谈虎色变 (tán hǔ sè biàn)
Long long ago, there was a farmer living in a small and tranquil village. One day, the poor guy was bitten by a hungry tiger when he went to the mountains to chop wood. Fortunately, he had a very narrow escape from the mouth of the awesome animal though it seriously hurt him. As the time elapsing, the wounds on the skin were healing day by day. But, nevertheless, that terrible memory lingered in his minds more than once. Some day, another resident in the village, surrounded with a host of people, was loudly talking something about the tiger. The farmer happened to passed by the crowds. His face turned totally pale the instant he heard the word “tiger”, which was all obvious symptom of considerable anxiety. Small wonder, he was more frightened than anyone else around since he had been badly hurt by one tiger. Afterwards, “to turn pale at the mention of a tiger” is used to refer that somebody becomes extremely nervous when he is informed of something that he once fell victim before.