Ganga Devi, the river Goddess prayed to Lord Siva to rid herself of all the sins that she had thus collected. Lord Siva directed her to Sri Vaanchiyam, which is situated on the way to Kumbakonam, Nannilam Nagapattinam, about 1 km from Acchuthamangalam. Ganga Devi is said to have bathed in the Gupta Gangai, the theertham in this temple & rid herself of her sins.
The Lord is Sri Vaanchinaathar. Brahma, Vishnu, Indran, Suryan, Yaman, Bairavar, Agni & other Gods & Devas have worshipped Lord Siva at this sthalam & got his blessings.
The great saints Gautamar, Jamadakni, Kaachiyabar, Athri, Viswamitrar, Baradwaajar, Vasishtar, Paraasarar, Vaalmiki, and others have received the blessings of the Lord here.
There is a separate sannadhi for Lord Yaman. Yama is the vahanam (vehicle) of Lord Siva at this temple. Every year during the month of Maasi, on the day of the Baranai star, the Lord is taken in procession on Yama vahanam. Devotees have to worship Lord Yama first at this temple before getting the darshan of the other Gods. Since Yaman is the Adi Devathai of Lord Saniswaran, obstacles due to Lord Sani can be reduced by offering prayers to Lord Yama at this temple.
This is also considered to be a shtalam for Kethu Bhagavan. Rahu Bhagavan & Kethu Bhagavan give darshan together. There is a separate sannadhi for Sani Bhagavan. Devotees bathe in the Gupta Gangai & offer special prayers during Raahu & Kethu Peyarchi.
The Chola, Pandya & Nayak rulers have contributed to the temple. The saivite saints Thirugnanasambandar, Thirunaavukarasar, Sundarar, Maanickavaasagar, Arunagirinathar, Raamalinga Vallalaar, Muthuswami Dikshitar have sung the praise of this Lord.