According to lengend, King Hung wanted to choose one son to succeed the throne. He called all his sons to come to him, and said that whoever could bring him the most precious offering to the altar of the ancestors, so showing all their pious feelings for him, would be given the throne.

All of the prices traveled throughout the country in search of the tastiest and  most exotic foods to offer their father, except Lang Lieu, the 18^th prince, who thought it over but had no idea where to begin looking.

One night, he dreamed of a genie that told him that “the rice grain is the most precious thing in the world. Now, you take the glutinous rice grain and make from it round cakes symbolizing the sky, and square cakes symbolizing the earth. The square cakes will have a filling made of peas and meat, and you will use green leaves to cover the cake, symbolizing the services rendered by fathers and mothers to their children. “When he awoke Lang Lieu was very happy and prepared the two kinds of cakes described by the genie.

When the day of the competition came, the King thoroughly examined the offerings of his sons, but he was not entirely satisfied. However, upon tasting Lang Lieu's cakes, the King congratulated and chose him to succeed his throne. Since then, the King and round glutinous rice cakes to offer to their ancestors on the occasion of the Tet holidays. Nowadays, these cakes are still a speciality for the whole country, any time of year.