The Chinese divides the whole year into 24 solar terms according to climate changes. Winter solstice, "the arrival of winter", is one, and it is the earliest recorded. It usually coincides with Dec 21 to 23 in the Gregorian calendar and is the shortest day of the year.

In the Chinese concept of yin and yang and the five elements, winter solstice is especially critical to maintaining yang qi, the masculine strength which keeps the body warm in winter. In the north, winter is all about fending off cold, and dumplings are eaten to dispel the chills and warm the body. More

But these small dough bags with fillings have varied names and styles in different places.