In medieval period Tamilians emigrated as soldiers, traders and labourers settled in Karnataka, Maharashtra, Sri Lanka, Thailand, Malaysia, Indonesia and intermixed well with local population, while few communities still maintain their language and culture.
During this period British, Dutch, French, Portuguese and Danish colony administrators recruited a lot of local Tamilians and took them to their overseas colonies to work as labourers, petty administration officers, clerical and military duties.
In the 19th century, Madras Presidency (of which the Tamil Nadu region was a core part of) faced brutal famines.
Britishers thus made use of Tamil workers for their plantations to all over the world - significantly in Malaysia, Mauritius, South Africa, Sri Lanka (distinct from the Sri Lankan Tamils) and also as far as Fiji, Guyana, Trinidad.
[1] There is also a group of people from French India colonies of Pondicherry and Karaikal which emigrated and settled in other parts of the world, significantly in France and its overseas territories (or former territories) in the Indian Ocean, such as Réunion and Seychelles, and the French Caribbean islands of Martinique and Guadeloupe.
These Tamilians well integrated, assimilated with their adopted countries, and became part and parcel of local populations in Mauritius, South Africa, Guyana, and Fiji.
In the second half of the 20th century, around 3.5 million Tamils emigrated from Tamil Nadu as skilled professionals, workers to various parts of India like Bangalore, Mumbai, Andaman Islands and also countries like UAE, USA, Singapore and so on.
[3] Portion of them trace their ancestry to the large number of Tamil speaking soldiers, suppliers and workers who were brought into the Bangalore Civil and Military Station, by the British Army, after the fall of Tippu Sultan.
There are about 450,000 Tamilians in the United Arab Emirates having come from Tamil Nadu as professionals and workers in many sectors.