Sundarban Forest, presently called 'Sundarbans National Park' in India, is a mangrove forest spanning the eastern coastal deltaic areas of West Bengal and western coastal deltaic areas of Bangladesh. UNESCO has declared it as a World Heritage Site. It is mentioned almost universally that the presence of 'Sundari' trees gave rise to the word Sundarban. A small question arises in the mind. If Sundari tree is at the root of the name, then would not the name have been Sundariban instead of Sundarban? Why the name had been changed to Sundarban? There is no apparent explanation for dropping the very important gender sensitive 'i' from the name. Exclusion of the letter 'i' makes the word from a feminine one to a masculine one. Generally, the prehistoric names don't change their names by the influence of the corrupted pronunciation practices of the commoners. Even if it is done, then also traces of the original names remain available from one source or the other. Nowhere it is told that the name of this forest was 'Sundariban' ever in the distant past. Always it remained 'Sundarban'. In that case there must be a source of this name that is independent of the word 'Sundari'. Naru, a Bengali by birth, has applied his acquired knowledge to find a logically consistent explanation of the name Sundarban. This book tries to provide the derivation of the name independent of the 'Sundari' tree.