I got the PDF file of the book Naag Sanskriti Kosh wirtten by Dr. Avantikaprasad Marmat. It is in Hindi. I found some names similar Nagavansha surnames. Our community's actual name is Nāgara. Our sacred scriptures Keralolpaththi and Keralamahathmya were written in Sanskrit thousands of years ago. Our community's name is given as Nāgara in these scriptures. When Kerala became a Buddhist region in third century B.C. Prakrit became the official language because Buddhist scriptures are written in Prakrit. Nāyara is the Prakrit word for Sanskrit word Nāgara. Hence, our community's got changed into Nair. There is a lake called Leelajan in Mahabodhi Temple. Its another name is Nairanjana which means sea of snakes.
Now I am going to share the names of snakes which I saw in that book and I found them similar to some Nair surnames. Some other communities too use these surnames but are not related to Illathu Nairs. (Click on the screenshots to make them appear alone on screen and click on the surnames, which are orange in colour, to read articles related to the surnames.)
1) Pillāyi - It is small venomous snake. It doesn't have a hood and it crawls speedily. To know more about this surname click, Pillai. Later Pillai became a title given by Pandya Kings to those men, irrespective of community, who worked as chieftains under them.
2) Pani - It is a name of a snake and also a species mentioned in Vedas. To know more about this surname click, Panicker.
. 
Bunt is another Hindu community found in the Tulunad region of Karnataka.
