During the time of King Hung-vuong, the Cao family had two sons who looked so much alike that no one could distinguish them apart. Their sagacious Teacher Luu asked his servants to bring a bowl of rice and a pair of chopsticks and called both of them to the table. Lang ceded the meal to his brother.  Thus, Teacher Luu knew that Tan was the older brother. He married his daughter to Tan. They were a well-assorted couple.  After the marriage, Tan was not as close to Lang as before. Lang was very unhappy with the sudden distant rapport between them. He left home and wandered around. One day, he came to a river. He stopped there to wait for a boat. He waited and waited, but did not see any boat. He died there and transformed into an areca nut tree. When Tan learn that his younger brother had left home, he went out looking for Lang. He went around, asking people about Lang. Finally, he was very depressed and stopped at the riverbank. He lamented the death of his brother and hit his head against the areca nut tree. He died and transformed into a limestone. Tan's wife was very worried. She went out searching for her husband. When she got to the riverbank, she was told that her husband and her brother-in-law both died there. She cried and clung herself to the limestone. She died and became a betel plant creeping around the limestone.

A few years later, King Hung-vuong passed by that riverbank. He was told of the story about the two brothers and the wife. He chewed come betel leaves with a piece of areca-nut and thought it tasted good. He spitted on the limestone and recognized that it turned into a deep red color. King Hung-vuong thought that the deep love between brothers and between husband and wife combined to yield that color. Therefore, he asked his people to build an altar for the three of them.

From that time on, people have known how to chew the betel leaves with areca-nut to redden their lips. At wedding celebrations, betel leaves and areca-nut become the customary present brought to the bridegroom's family. Betel leaves and areca-nut are also used as snacks for the guests. Thus, one of the Vietnamese saying is “Some betel leaves can be the introduction to a conversation."