In ancient times, people used a brush to write, but before using the brush, they usually soaked the brush in water to make the hair of the brush open and soft, so that the brush could absorb ink more easily and feel more round when writing. Therefore, the action of soaking the brush in water is called "moistening the brush". Later, "run pen" generally refers to the remuneration for inviting people to write articles, writing and painting.
The word "Runbi" originated from a short story between Zheng Yi and Emperor Wen of Sui Dynasty in the Northern Zhou Dynasty. Later generations regard the collection as elegant. Nowadays, it is mostly used to refer to the remuneration earned by calligraphers from selling calligraphy and painting, and the custom of calligraphers ordering embellished calligraphy has also been widely accepted by the society.