This is named after the Kaisika Puranam which is 48th Chapter in Sri Varaha Puranam. In the Varaha Puranam, Lord Vishnu tells the story to Mahalakshmi about how he adores being worshipped through dance and music.

Kaisika Ekadesi is celebrated in the Tamil Month of KArthigai on the succeeding Ekadesi in the Sukla Paksham.

TiRukarungudi Deity Nambi used to listen to the ghAnam of a great bhkatA called NampAduvAn. He was born in chandala kulam. On every Kaisika Dwadesi day, Nambaduvan, used to sing for THE Lord at Thirukurungudi.

The main incident is of Nambaduvan being confronted by a Brahma Rakshasa. This Rakshasa used to be a Brahmin by the name of Soma-Sharma. He committed some grave mistakes during a Yagam and was cursed by which he became a Brahma Rakshasa.

On Kaisika Ekadesi day, he was traveling to the temple when a Rakshasa (demon) stops him and demands his flesh. After great persuasion, Nambaduvan tells the Rakshasa that he would return to be eaten by him after completing his annual offering of music to Nambi Perumal. The Rakshasa allows him to proceed to the temple. After singing all night in front of the Lord, Nambaduvan is on his way to the Rakshasa to fulfill his promise. At that time, Lord Vishnu himself, in the guise of an old man, stops him and asks him to take another route, warning him of a dangerous Rakshasa who eats all in his path. Nambaduvan refuses to break his promise and proceeds to meet his death. The Rakshana was surprised to see him coming back there. He now demands that Nambaduvan give over to him not his physical body but the Punyam (fruits of good deeds) he has acquired from his musical offerings to Nambi Perumal. Nambaduvan refuses and explained that he did not sing by expecting anything in return (punniam), just for the pleasure of praising the Lord Nambi. But he could worship to Lord to protect the Rakshasa from the curse. As he prayed Rakshasa was relieved from the curse.
After many thousands of years, on a Kaisika Dwadesi day Sri Parasara Bhattar (about 900 yrs ago) chanted the Kaisika Puranam before NAMPERUMAL with his vyakhyanam (explanations).