Marundeeswarar is known so because Shiva imparted sage Agastya on curative properties of various herbs and plants. Since then the Marundeeswarar temple has been a place of worship for people with diseases and various problems with their health. It is said that even The Sage Valmiki, who wrote The Ramayana, came here to The Marundeeswarar temple to worship Shiva. Sage Valmiki was said to be blessed here. After this incident, this place was to be known as Thiruvalmikiyur, the name gradually changed to Thiruvanmiyur. Inscriptions can be found in the shrine of Tripurasundari Amman dating back to the 11th century during the period of Rajendra Chola. Legend Is, Recognizing the penance of Sage Vasishta on Lord Shiva, Indra sent his Kamadenu the divine cow with the sage.  Once, the cow delayed to pour the milk for puja.  The angry sage cursed it to become an ordinary cow losing its divine status.  He also suggested the cow to go to this place and worship Lord Shiva under the Vanni tree to recover its divinity.  Kamadenu poured the milk on the Lord and got back its original supremacy.  Hence, the Lord has the name Paalvanna Nather.  Paal in Tamil means milk.  When Sage Valmiki came there to worship Lord Shiva, Kamadhenu ran in fear pressing its feet on the head of the Shiva linga, the scar of which is still visible on the presiding deity.