Idangai or the left hand is a caste-based division of communities in Tamil Nadu that was in vogue from ancient times right up to the 19th and even the early decades of the 20th century AD.
From ancient times, there was intense rivalry between the left-handed and right-handed factions.
Some castes considered to be left-handed in some areas were regarded as right-handed in others and vice versa.
[4] Roughly speaking, the Valangai or right-handed faction was made up of castes with an agricultural basis while the Idangai was made of metal workers, weavers, etc.
[5]The core groups in Idangai were the five castes called Anchalar/ Panchalar.