As per Hindu legend, Vishnu in the form of tortoise (called Karkada) worshiped Shiva to attain divine ambrosia at this place. On account of the legend, the place was called Kascapavoor, which went on to become Kachoor and the presiding deity, Shiva came to be known as Karchabeswarar. As per another legend, Vishnu appeared in the form of Matsya appeared from the Ocean of Milk to help the Devas. Vishnu appeared in this place, created a spring, bathed and prayed to Shiva at this place. Since Shiva helped Vishnu, the place came to be known as Tirukachur. As per a third legend, Indra, the king of celestial deities got a disease which could not be cured by the physicians of the celestial world. The Ashwini Devas of the celestial world also could not cure the disease. With the help of sage Narada who advised them to worship Shiva, they were able to find the herbs in earth that could cure the disease. Indra was cured with the herb, but they were not able to find the place where they found the herb in earth. They prayed to Parvathi who appeared in the place in the form of Irulneeki Amman (the one who cleared darkness) and directed them the place. The temple has a recorded history from the 10th century, but scholar attribute the presence of the temple at least from the 8th century, pertaining to the period of Sundarar, the famous Saiva Nayanar. Sundarar has glorified the temple in his verses in 11th Thirumurai of Thevaram.