Warrior tribe of Kosars have been cited in ancient Tamil Sangam literatures. Kosars are described as a honest warrior tribe who were known as ‘one word kosars’(“Onrumoli Kosar” in Tamil) because they always kept their words (promises).
Wayfarer in his blog has made a decent documentation of distribution of known Khosa tribes. The ancient tribe were variously known as Khosa or Kosar, Kossar or Khasa.
In some Tamil accounts, Kosars belonged to the Tulu country and lived to the south of the Vindhya and near the shores of western Arabian Sea. They were also referred to as ‘Ariyar’ in Tamil literature.
Kosars have been recorded as tribal people who lived near the rivers Malprabha, Gatprabha and upper the border area between Kadamba and Mauryan empire. They attacked Paazhi and captured the whole of Kadamba and its many fort cities. Then the Mauryans and their Kosar affliates entered Tamil Nadu through the kaviri-kudhirai malai pass (the present anthiyur-nallur path).
The District Gazetteer of South Kanara (1973) enlists Koosa as a Scheduled Caste tribe. This Koosa tribe is being speculated by tulu-research.blogspot.com as the Kosar tribes of Karavali described in the Tamil Sangam literature.
The name 'Kochati' also appears to be related to the words 'Kocha'(singular) or 'Kochar'(plural). Incidentally, Kochati is a place name in Nicosia, Cyprus. Similarly, there is a Kochati (also known as Kochadai) in Madurai. These could be ancient ethnonyms.
Similarly, Kochi is an important town in Kerala; this place name is possibly related to these tribes.