The legends of early Vietnam.
According to legend, the first truly Vietnamese king was Lac Long Quan, also known as the “Dragon Lord of Lac”, whose home is the sea of what is now Northern Viet Nam. Lac Long Quan married a princess from the mountains, named Au Co, and their union resulted in a 100 eggs. From each of these eggs, a son was born, giving Lac Long Quan and Au Co 100 sons. But as one is from the sea and the other from the mountains, Lac Long Quan and Au Co soon separated. Lac Long Quan took with him 50 sons back to the lowlands and they became known as the people of Lac Viet. Au Co took 50 sons with her back to the mountains and high-regions and became the people of Au Viet.
Legend continues that Lac Long Quan’s eldest son succeeded him to become the first King Hung Vuong. King Hung Vuong joined all of the people of Lac Viet together and created the kingdom of Van Lang. After 18 hereditary kings of the King Hung Vuong dynasty, Van Lang was invaded by the leader of Au Viet, Thuc Phan. Thuc Phan successfully united the Lac Viet and Au Viet, proclaimed himself King An Duong Vuong, and called his kingdom Au Lac to signify the union of the two.
Throughout history, there have been many names for the land that is now known as Viet Nam. In the beginning, there was the kingdom of Van Lang, which later became the kingdom of Au Lac. Au Lac shortly thereafter became Nam Viet, then Giao Chi, Van Xuan, An Nam, Dai Co Viet, Dai Ngu, Dai Viet and finally Viet Nam.
And that is why to this day, many Vietnamese people consider Lac Long Quan and Au Co as the primal ancestors of the country of Viet Nam.