What the ancients escorted in groups was called an outline.

Birthday means birthday.

Then the things that are escorted by groups on birthdays are called birthday classes.

Interpretation of the second article of the "Outline" of the Dictionary of Common Words in Ancient Chinese: the organization of transporting goods in batches during the Tang and Song Dynasties. Such as "salt", "tea" and "flower stone"

The story of eight heroes, such as Chao Gai and Wu Yong, who couldn't beat the birth outline is a story of robbing a motorcade, so that's what it means.

Birthday class is a collective transportation of goods to celebrate birthdays.