The Theertha Kulam is opposite of Lord Sundareswara where the float festival takes place on the 11th day of Chithirai festival in April-May. This is the best place to offer children facing adverse planetary aspects to Lord in adoption. While doing so, the parents should not have any prayer commitment due in other temples. If so, they have to fulfill it and then only do the adoption ritual in this temple. Thus, Lord Sundareswarar facilitates fulfillment of prayer dues to other Gods in other temples.
While offering the child in adoption, parents vow saying with tears in eyes that they sell the child to Lord under a document – Suddha Sasana Kirayam - and hand over the child to the priest. The priest in turn gives the child to the grandparents or to the maternal uncle. When the child attains the marriageable age, the parents come back to the Lord, tell Him that they withdraw the adoption and take the boy or girl back.
Ari means Moon. Mazha means child. Due to a curse, Moon began shrinking and reached child size. Moon came to this place dense then with vilwa trees and prayed to Lord. Lord wore the child moon – crescent moon – in His head and thus the curse of moon vanished. He begged Lord that the place be known as Arimalam which the Lord granted.
According to other story, Arum Pallam would have changed as Ari Malam. One more story is that a rare variety of fruit called Eranji Pazham in the Vilangi Amman shrine got the name Arum Pazham meaning rare fruit which later shrunk as Arimalam, according some researchers.
The rays of Sun fall on the Shivalinga in the temple from March 19 to 21 when special pujas are dedicated to Lord.