Wikipedia
In Hinduism, Shesha ( Sanskrit: ), also known as Sheshanaga or Adishesha , is the nagaraja or king of all nāgas and one of the primal beings of creation. In the Puranas, Shesha is said to hold all the planets of the universe on his hoods and to constantly sing the glories of the God Vishnu from all his mouths. He is sometimes referred to as Ananta Shesha, which translates as endless-Shesha or Adishesha "first Shesha". It is said that when Adishesa uncoils, time moves forward and creation takes place; when he coils back, the universe ceases to exist.
Vishnu is often depicted as resting on Shesha. Shesha is considered a servant as well as a manifestation of Vishnu. He is said to have descended to Earth in two human forms or avatars: Lakshmana, brother of Rama; Balarama, brother of Krishna.
"Shesha" in Sanskrit texts, especially those relating to mathematical calculation, implies the "remainder" — that which remains when all else ceases to exist. But in Sanskrit it also means 6 shesham as the sheshanaga has been depicted to have many heads (5 to 7).