Iyers is a colloqial term which was used to refer to tamil brahmins.In latertimes, when many vaishnava sects proclaimed themselves Iyengars, the word Iyer was used to usually refer to either saivaites or to smarthas. They are usually smarthas and follow Adi Shankara's teachings. Their puja consists of the one or more of the five principal deities (Panchayathana puja) - Ambal (Shakthi), Shiva, Vishnu, Ganesh and Surya. Other deities like Murugan (part of Shiva), Lakshmi (cannot be separated from Vishnu), etc. are indirectly part of this. Besides this they worship other deities , as recorded in the Vedas such as Indra, Agni, Yama etc. They also practice Ancestor worship and also worship Rishis who were involved in the composition/revelation of the Vedic books.

While there are no specific historical accounts or documents which describe them having come from distant lands, traditional folklore records that Agatsya was the founder of Tamil Culture. Siva Purana suggests that he learnt Tamil from Lord Shiva and brought the language to the south. This legend is found in the Tamil-language Shivapuranam.) Many Iyers reject this theory, as they believe that there are no historical records or folklore that suggest and invasion in south. There are a number of other theories based on race, caste and invasion, which are yet to be proven or substantiated by any verifiable or authentic evidence.