Listen to this article这个典故，被大家用“羊质虎皮”这句话来形容，表示外表好看，里面却空虚而不实际的意思。比较简单而完整的解释是这样的：用来比喻蒙上一层虚伪欺人的外表，而实际却是一个空虚无力的人。这句成语应用的范围非常的广泛，像市井中的无赖，平日作威作福，专门欺侮善良的人，等到被欺侮的人忍无可忍，要和这个无赖拼命的时候，无赖反而畏缩逃走，这种欺善怕恶的无赖，就可以说是“羊质虎皮”的人。
《古代寓言·羊质虎皮》
羊质而虎皮，见草而说，见豺而战。忘其皮之虎矣。——《法言》
The Lamb in a Tiger’s Skin
Once a lamb clad itself in a tiger’s skin.
As it was stalking along, it bleated joyously at the sight of the green grass, but when it saw a wolf in the distance it trembled all over.
The truth is that the lamb had forgotten that it had the tiger’s skin on
