In olden days Arni was called Aranyam. The word Aranyam is now only called as Arni.The word Aar means Athi tree. Once upon a time this region was surrounded by full of Athi trees. Also in the north of Arni, there was a river by name Kamandala Naga river. These trees and river look like an ornament hence the name Arni. Arni was ruled by Cholas after they defeated Pallavas. Some of the important Chola kings who ruled out Arni are First Kulothunga Cholan, Vikrama Cholan, Second Kulothunga Cholan, etc. During the rule of Vijayanagara Kingdom at Arni, Dasara function was celebrated grandly. Poosi Malai Kuppam is 12Kms away from Arni. Thirumalai Saheb builta Sophisticated bungalow for his lovable Anglo-Indian lady there. During Navab's period there was a struggle between Britisher's, Frankians and Nawab Hyder Ali. Finally Britishers won the struggle and they captured Arni. There is also a Palace near by town, which is now used by the Agricultre Department.