The sthala puranam for this divya desam is mentioned briefly in Brahmanda puranam. Once the Moon God, Chandran, was cursed and day by day, his charm was waning. He reached this sthalam and was in a very sad moon not knowing how to get rid of the curse. Seeing Chandran's plight, Perumal appeared before him and relieved him of the curse. Perumal is also believed to have appeared before Deva Brindangar, but no details of this event are available at this time. The sad posture of Chandran is known as Naani in tamil. Hence the Perumal who blessed Chandran is known as Naan Mathiya Perumal.

Once this place was a thick forest, and due to its proximity to Kaveripoom pattinam, then a popular town known for its Chnagu industry, this place is known as Thalai changu kadu (thalai here refers to prime position of importance). It is also believed that the Changu the Perumal holds is unique and beautiful, not found in other temples, and hence the name Thalai changu kadu.








Source:
1. 108 Vasihnavaite Divya Desam by Miss M. S. Ramesh.