According to legendary story this shrine was consecrated by a Rishi by name SWETHA MUNI. The legend is that AGASTHYA MUNI on his way to Kaveri River for offering his customary ablutions was once confronted by two demons namely NEELAN and SWETHAN. The Muni cursed them.On request for penance, they were advised to perform TAPAS at two Siva Temples. They were later known as Neelarshi and Swetharshi. The places where Neelarshi and Swetharshi performed their Tapas came to be known as Neeleswaram and Swetharanyapuram respectively. The latter was a dense forest at that time. The present name Thiruvangad must have been derived in this connection. It is said that Swetharshi consecrated a Vishnu temple also (dedicated to Sree Rama) at the site where he performed his Tapas. Another version of the legend says that Siva Temple was consecrated by Neelarshi - a Shiva Bhakta and Sree Rama temple was consecrated by Swetharshi - a Vishnu Bhakta. The chief deity carved out in Krishna Shila is Sree Rama reverently referred to by local people from time immemorial as Perumal.