Island
An island or isle is any piece of sub-continental land that is surrounded by water. Very small islands such as emergent land features on atolls can be called islets, skerries, cays or keys. An island in a river or a lake island may be called an eyot or ait, and a small island off the coast may be called a holm. A grouping of geographically or geologically related islands is called an archipelago, such as the Philippines.
Lanka
Another theory states that the word "Lanka" simply means any island. It is still widely used by the aborigines of Central and Eastern India to mean an island and especially an islet in a river. The word is considered as belonging to Austro-Asiatic languages. The Veddas, the aborigines of Sri Lanka who might be of Austro-Asiatic origin, might have rendered the name "Lanka" to the island. As it is the biggest island in the South Asian context, "Lanka" probably became an exclusive term for it.