Koothanallur derives its name from two cultivator-brothers called Younger Koothan and Elder Koothan who are believed to have been the original settlers in the patch of wet lands some 700 years ago. "Nallur" denotes the welfare status of the village those days. The present Koothanallur is a municipal town of 12.31 square kilometres in area, lying on the route between Mannargudi and Tiruvarur of old East Tanjore District, some 350 kilometres south east of Chennai. It is populated predominantly by Muslim community. River Vennar which flows through the heart of the town keeps the soil most fertile.