Vata – a name of the Banyan Tree
Patra – Leaf
Sayi – the resting one

Krishna, as a child, lying on a floating banyan leaf in the ocean, sucking on his toe.

There are a number of not necessarily coherent stories about this depiction.

Krishna wondered why the sages refuse nectar and prefer to drink the water that has been poured over his feet. He sucked on his toe and tasted the sweetness of the toe.

Krishna as Vatapatrasayi continues to be associated with the dissolution of the universe, Pralaya. In this case Vishnu takes the form of a child and does not float on the cosmic waters on Shesha, but on a banyan leaf. He swallows the universe, holds it in his stomach and ’spits‘ it out at the time of the new creation.