Kerala Iyers, colloquially called Pattars, are Tamil

Tamil people

Tamil people , also called Tamils or Tamilians, are an ethnic group native to Tamil Nadu, India and the north-eastern region of Sri Lanka. Historic and post 15th century emigrant communities are also found across the world, notably Malaysia, Singapore, Mauritius, South Africa, Australia, Canada,...

 Iyers of the Indian state of Kerala

Kerala

or Keralam is an Indian state located on the Malabar coast of south-west India. It was created on 1 November 1956 by the States Reorganisation Act by combining various Malayalam speaking regions....

 who migrated from present day Tamil Nadu

Tamil Nadu

Tamil Nadu is one of the 28 states of India. Its capital and largest city is Chennai. Tamil Nadu lies in the southernmost part of the Indian Peninsula and is bordered by the union territory of Pondicherry, and the states of Kerala, Karnataka, and Andhra Pradesh...

 in different waves starting from the medieval period onwards. The community consists of two groups - the Palakkad Iyers and Iyers of the Cochin ad Travancore regions.

The first wave of Iyers settled down in Palakkad district at the beginning of the medieval period.