Long ago, this place was known as Kedara Nilayam. A sage named Suprapar was clearing the land here to perform a Yaga. He unearthed a balance (Tharasu) and a bow (vil). The moment he touched them, they turned into a young woman and a man respectively. They said that their names were Thulai and Villi and due to a sin committed against Lord Kubera, they were cursed; the redemption of which was by the touch of sage suprapar. The Sage completed the Yaga, gave the benefit (Havis) to Devas and prayed to Perumal who gave his Darshan here. Sage Suprapar requested that Perumal be known as Devapiran and the place be known as Thiru Thulai Villi Mangalam. These were conceded by Perumal.
Sage Suprapar continued his Poojas at Thiru Thulai Villi Mangalam. He used to offer lotus flowers to Perumal. Perumal loved such beautiful flowers and wanted to see from where they were collected. One day, Perumal followed Sage Suprapar. On reaching the bank of a very beautiful tank and seeing it full of lovely lotuses, He decided to stay there. Sage Suprapar wondered why God had followed him. God said that He loved lotus flowers and whoever worships Him with a lotus, will earn His blessings. God also said that He shall henceforth, be known as Aravintha Lochanar. Thus, Sage Suprapar started worshipping Perumal in two forms (Erattai Thiruppathi).
Yet another story, connected to this place, relates to the name of the tank. Once Aswini Devas (Two Devas) were not getting a share (Havis) of Suprapar’s yaga. They requested Lord Brahmma’s help and he advised them to worship Perumal at Erattai Thiruppathi. Aswini Devas reached this place, took regular bath at this tank and did penance. Perumal was pleased and conceded their request. Perumal added that as Aswini Devas took bath here, this tank would henceforth be known as Aswini Theertham. There is one more story about the holiness of this Theertham. One Brahmin named Vibeedhakan was afflicted by leprosy. His brothers sought Lord Naradas help. He advised them to go to Thiru Thulai Villi Mangalam and to worship Perumal. The brothers did so. In course of time, due to regular bath at Aswini Theertham and their worship to Perumal, Vibeedhakan was cured of leprosy.