His unfeigned surprise showed clearly on his face.

unfeigned 是由前缀 un-（表示"不、非"）和动词 feign（假装）的过去分词 feigned 组合而成。feign 本身源自拉丁语，意为"塑造、假装"。 unfeigned 字面意思是"没有假装的"，引申为"真诚的、真实的"。在句中形容惊讶是发自内心的真实反应。