The name Kerala has an uncertain etymology. One folk etymology derives "Kerala" from the Malayalam word 'coconut tree' and 'land'; thus, 'land of coconuts', which is a nickname for the state used by locals due to the abundance of coconut trees. The word "Kerala" is first recorded as "Ketalaputo" ('son of Chera') in a 3rd-century-BCE rock inscription left by the Maurya emperor Ashoka (274–237 BCE), one of his edicts pertaining to welfare. This contradicts the theory that is from 'coconut tree'. At that time, one of three states in the region was called Chera Dynasty in Classical Tamil: and are variants of the same word. The word refers to the oldest known dynasty of Kerala kings and is derived from the Proto-Tamil-Malayalam word for 'lake'.