Beside the temple religion of the south runs a stratum of village deities, most of them goddesses, who are territorial rather than universal, are concerned with disease, protection and boundaries, and are served by non brahmin priests. Mariyamman, associated first with smallpox and later with fever generally, is the most widespread. These cults are older than, and largely independent of, the Sanskritic tradition layered above them, and they remain the ordinary religion of a great many villages.
Dravidian as a category also became a political identity in the twentieth century. The Dravidian movement in Tamil Nadu, associated with Periyar E. V. Ramasamy, mounted a direct attack on brahmin authority, on Sanskrit and on the religious hierarchy attached to them, and it produced an explicitly rationalist and often atheist politics that has governed the state for decades. Temple entry legislation and the appointment of non brahmin priests followed from it.
The atlas records this because it is a case of a linguistic classification becoming a religious and political programme, which is exactly the movement it warns against elsewhere. Here the direction was reversed. The family name was taken up by the people it named, and used against a religious hierarchy rather than to construct one.
Sources A Temple Festival of MariyammanPaul Younger with Periyar: A Study in Political AtheismKarthick Ram Manoharan