Nadar caste was recognized as Shanars till the 19th century. Thereafter they came to be known as Nadars which was derived from the Nandans, the supreme head of this community. The origin of the caste as a social group is anonymous. However historians believe that they are the descendants of prehistoric rulers like Cheras, Cholas and Pandyas. There is not much evidence to support this claim.
The community was previously known as Shanar but legally changed their name to Nadar in 1921. The title Nadar is believed to be derived from the Nelamaikkarars, the aristocrats of the Shanar community who had previously used it exclusively. Nadars claim that the original name of the community was Shantror or Shandrar (noble one) which, in course of time, was corrupted to Shanar. Channar is a title used by the Ezhava community of Kerala. However, there is no evidence to support these claims.
The origin of Nadars as a social group is uncertain. Hardgrave stated that the Teri palmyra forests around today's Tiruchendur must have been their original abode.In the late 19th century, some Nadar activists started claiming that the Nadars are the descendants of those who ruled the Pandyan kingdom and that when Nayak rulers captured the Pandya country, it was divided into several Palayams (divisions) for each of which Palaiyakkars were appointed as rulers. They also claimed that the Nayak rulers of Tamil Nadu imposed Deshaprashtam (ostracism) on the ancient Nadars to ensure that they would not rise.