Lushan (Mount Lu) acquired its name because a hermit named Kuang Su built a hermitage there during the reign of King Wu of Zhou. The mountain is surrounded by rivers on three sides, presenting a majestic and magnificent landscape with verdant mountains and clear waters.

Due to its proximity to the water and the frequent mists and clouds that envelop its peaks, people found it challenging to discern its true appearance. The famous Song Dynasty poet Su Shi beautifully captured this phenomenon in his poem "題西林壁" (Title on the Wall of Xilin Temple): "From the side, a peak; from the front, a range; far or near, high or low, no two views are the same. I cannot discern the true face of Lushan, for I am myself within the mountain."

This idiom thus metaphorically describes the difficulty of recognizing the truth or essence of something when one is too entangled in it or lacks an objective viewpoint.