During the Southern and Northern Dynasties (420-589), in the reign of Emperor Wu of Liang, there was a highly accomplished monk named Master Yun Guang. Once, he explained the Buddhist sutras with such profound and subtle insight that the Flower Deity was moved and sent divine blossoms showering down to earth. Soon, the ground was carpeted with flowers.
This idiom is later used metaphorically to describe speech that is vivid and eloquent, often in an exaggerated or impractical manner.