It comes from "Cang Dog Changfeng" by Wang Zhongwei, a poet in the Song Dynasty.
"A Gray Dog Changing the Wind": Light joy is like a gray dog, deep love is like a long wind. My love is separated by mountains and seas, and I hope the mountains and seas can be leveled.
The meaning of the poem is: A superficial liking for a person may disappear at any time just like the white clouds in the sky. Having deep love for someone is like the gentle wind, accompanying them silently and silently anytime and anywhere. There are overlapping mountains and deep seas between me and the one I love. Although the mountains cannot be eliminated and the sea cannot be filled, I will still guard her silently like the long wind. Extended information
Baiyun, Canggou
"Baiyun" means "Canggou", and "Canggou" means "Baiyun". "Baiyun" is the name and expression of modern people's name for clouds. "Canggou" is the ancient people's name for clouds. Today's idiom "white clouds and cangou" is used to describe that everything in the world is as unpredictable as the white clouds in the sky.
Du Fu, a poet of the Tang Dynasty, had this sentence in his poem "Sigh": "The floating clouds in the sky are like white clothes, and the changes here are like gray dogs." "White Dogs" came to lament the changes in the world. , difficult to guess. But it is generally called "White Cloud Dog". Therefore, modern people also use "White Cloud Cang Dog" as "White Clothes Cang Dog". Both idioms have the same meaning, and they both use the unpredictability of white clouds to refer to the ever-changing world.
References Baiyuncang Dog-Baidu Encyclopedia