The word comes from the Sanskrit, an ancient Indian Language:

Well you may have doubts here that another article in the same web page which says that Mridhangam is made out of Jack wood etc., then how is it that the name derived as above. In the olden days the instrument was actually made out of Clay as it was cheaply available and also there were not too many artisans to cut wood and carve them in to the shape of a mridhangam. But at a later stage the instrument made out of clay made way to wood due to various factors like Weight of the instrument and also its maintenance. The instrument made out of clay, if handled carelessly, could break like a clay pot. So based on the necessity wood replaced clay and it is still being used till date. Though there are still further enhancements and researches are made to replace the wood with Fibre Glass, yet there has been no comprehensive and convincing replacement to claim universal acceptance amongst mridhangists. Some of the mridhangists now prefer Fibre Glass instruments to wooden instruments mainly because of its weight and easy handling. But traditionalists and puritans still believe in Jack Wood instruments as it has brings the natural tone and sound to the instrument. The choice is left to the individual.