In the Spring and Autumn Period (770-476 BC), there was a beauty in the State of Yue called Xishi (西施). She often suffered from pains in her chest, and so she would often walk around doubled over and with her brows knitted. There was an ugly girl in the village called Dongshi who envied Xishi. Striving to emulate Xishi, she imitated her stoop, knitting her brows at the same time. She thought that this made her elegant, but in fact, it only made her more ugly.

Later, this idiom came to be used to indicate improper imitation that produces the reverse effect.

西施是中国历史上的“四大美女”之一，是春秋时期越国人，有心痛的毛病。犯病时手扶住胸口，皱着眉头，比平时更美丽。 同村女孩东施学着西施的样子扶住胸口，皱着眉头，因其本来就长得丑，再加上刻意地模仿西施的动作，装腔作势的怪样子，让人更加厌恶。

东施效颦：比喻模仿别人，不但模仿不好，反而出丑。