Not many people know that a large population of Kannada Kurubas live in Tamil Nadu, the region surrounding the Nilgiri Hills all the way down the Western Ghats on the Tamil Nadu side. They have their distinct costumes and culture. The most important thing which differentiates them from the rest of the people of Tamil Nadu is their language, they speak Kuruba Language a dialect of Kannada. Even though they have been Tamilised due to living in Tamil surrounding areas , they still manage to speak Kannada with a Tamil accent though.
According to some unofficial estimates their population is around 40 lakhs, which is a good number. These Kurubas are descendants of the Pallavas, after the fall of the empire they took shelter in the forests surrounding the Western Ghats, as a precaution and survival tactic from their enemies, this move of taking shelter in the foot hills of western ghats took their civilisation backwards from the peak during the Pallava Period to the present day low. These Kurubas don't have any connections with their brothers in Karnataka, this link was lost long time ago and the Tamil Nadu Kurubas have their own rich history and traditions. This also points towards an argument that the founders of Pallava dynasty may well have been Kannada speaking Kurubas who gradually took up Tamil.
Then their is second group of Kurubas in Tamail Nadu who are found again in districts bordering Karnataka, they might have been the recent immigrants or settlers who went there during the rule of Mysore Maharajahs, Mysore rule went down south as far as Salem in Tamil Nadu. These Kurubas were local chieftains and feudal lords of the Mysore kingdom and many have the surnames as Hegde or Gowda. Then there is still recent Immigration of Kurubas to Tamil Nadu mainly Chennai, which started after Independence, and as far as I know there is a street named Kurumbar Veedhi near Triplicane, Chennai. People in Karnataka should show a bit more interest and support their fellow Kannadigas who are still living a life of poverty in the neighbouring Tamil Nadu.