When Lord Shiva and Devi Parvati got married in the Himalayas, the Northern portion became heavier because of the massive congregation for the divine wedding. In order to maintain balance of the Earth, Lord Shiva sent sage Agastya to the South promising to give him darshan in the South in Their wedding glory. It is believed that the Divine Couple, as promised, gave darshan to sage Agastya here in Tirunelveli. The sage also got such darshan in other places like Thirumaraikaadu, Thirunallur, Papanasam and a few other shrines. Legend of Nelliappar: A pious priest of the temple used to collect paddy from nearby houses and make food offerings to Lord Shiva. Once he dried paddy in front of his house and went for bath in the nearby Thambraparni river. Suddenly it started raining. The priest came rushing to save the paddy from getting wet. But even before the priest reached the spot, Lord Shiva, in order to bless His staunch devotee, prepared a Veli (fence) for the Nel (paddy) and saved the paddy from being washed away by rainwater.
The towns name Tiru-Nel-Veli (Tiru being the Tamil prefix to address holy places or names) and that of the Lord (Nelliappar) are attributed to this incident.
Legend of Venuvana Nathar: The Lord here is also known as Venuvana Nathar. Legend has it that Lord Shiva manifested Himself as a Swayambu Linga (self-created) in a bamboo forest. Once a milkman by name Rama Konar, while passing through this area, stumbled on some object and dropped his milk pot. To his surprise, this was happening to him every day at the same spot. One day when he tried to clear the bamboo trees, his axe hit a stone and blood started oozing out. He alerted the villagers, who found a Linga amidst the bamboo trees. The bamboo trees are believed to be the manifestation of the Vedas. Hence the Lord is known as Venuvana Nathar (Lord of Bamboo Forest - venu means bamboo and vana is forest).