I am a Malayali, and I believe I can speak for this from my own experience.
Malayalis in the past, especially those from higher castes, had a sacred grove in the southwestern corner of their traditionally huge plots of real estate (often 2-3 acres in size). They were called kaavukal (singular: kaavu). These were left unvisited at most times of day and treated akin to temples. The members of the household may visit the grove in the morning after a bath, pray silently, and wear prasadam . They were always left in silence, and it was considered unbecoming of one to make noises here.
Kaavukal were always dedicated to snake-gods, and were called sarpankaavukal  too, for this reason. The legend goes that when Parashurama created the Malayaladesham by throwing his axe across the ocean, the land that rose up was inhabited by snakes. The Brahmins who had concurred to settle there were advised to worship these snakes and live amongst them. Snakes and Malayalis are thus bonded. Even the moorthi of Lord Vishnu at the Padmanabhaswamy Kshetram in Thiruvananthapuram is that of his anantashayanam .
As landholdings in Kerala shrunk, the kaavukal came to be cleared off. A special puja was usually conducted to lift the serpents off the kaavu. Following this, the members of the household visit a temple, usually the historic Ameda Sarpa Kshetram in Kochi and permanently place the serpents there. This ritual is called sarpamiruthal .
- In Malayalam, prasadam refers to both the food blessed at temples, and the tilakam or chandanam that Hindus wear on their forehead.
- Sarpankaavu = sarpam + kaavu, a sandhi that literally means "grove of serpents".
- The anantashayanam is Vishnu's shayanam (rest, sleeping) on Ananta, King of Serpents.
- Sarpamiruthal = "seating the serpent".