Lu You
The beizi originated in the Song dynasty; it is assumed that it was derived from the banbi, where the sleeves and the garment lengthened. According to Ye Mende, the beizi was initially worn as a military clothing with "half-sleeves"; the sleeves were later extended and hanging ribbons were added from the armpits and back. In earlier times, the beizi did not exist according to both Zhu Xi and Lu You, and it only became popular by the Late Northern Song dynasty.