Depending on the path they chose to migrate the Kerala Iyers are divided into Palakkad Brahmins and Pandikkars. The Palakkad Brahmins migrated via the Palakkad pass and the Pandikkars (meaning those belonging to Pandya Nadu) migrated via Shenkottai (Aruvamozhy pass). The other wave of migration was from Tirunelveli and they maintained a separate identity. It is strange to note that though both these districts belonged to Pandya Nadu, the people who migrated from Tirunelveli consider those who migrated from Madurai as Pandikkars. They say that this sect is not through out Travancore state but in pockets around Cochin.
Till recently the identity of these groups were maintained. Cross marriages between these groups were uncommon. The Samoohams were separately maintained in towns where there is considerable population of both these groups, e.g., in Trichur, Irinjalakkuda, and Ernakulam. Most of the sub groups of Iyers like Vadamas, Brihatcharanams, Vathimas, Ashtasahasram, etc are represented among Kerala Iyers. Those belonging to Krishna Yajurveda etc. are also represented. Vadamas means those from North and Brihatcharanam means 'Big step'. Most of the Kerala iyers belong to these two groups. The other numerically powerful group is Ashtasahasram who have migrated from a village called Ennayiram in Tamil Nadu.
The Iyengars are normally absent but there are Vaishnavite villages in Pallipuram, and Thirunellayi. The Iyers of these villages wear a red line (Urdwa Pundram) as against the Vibhuthi of other iyers. They also did not have "Paramesawar Preetyartham" in Sankalpas but used to perform Viswaksena Pooja instead of Ganapathi Pooja. But over years due to possible reason of non-availability of priests, they perform their rituals similar to other Smarthas. It is important to note that their womenfolk always used to wear the ritualistic Sari measuring 9 yards similar to Iyers and not Iyengars. They also did not follow Ramanujacharya but were followers of a rebel group of Vaishnavas belonging to Ahobila.
There are two more groups of Vaishnava smarthas (research has indicated that early Vadamas preferred to wear Gopi Chandana instead of Vibhuti) in Kerala; they wear Gopi Chandana in the pattern of Madhwa Brahmins of Karnataka who speak tulu and the long Gopi Chandana mark like the Marathi Brahmins round about Pandarpur.
Another interesting group is Chozhiyans. People say that they originated from Chozha Desa but the fact is that they are a sub group of Brahmins called Sholiyars who claim that 'The Great Chanakya' of Chandra Gupta's court was one of them. They were generally temple priests by profession. They also are supposed to have officiated as priests in functions of non-Brahmins. These Brahmins have tuft in front of the head similar to the Namboothiris or the Chidambaram Deekshithars. There is a proverb among Kerala Iyers that "Chozhiyan Kudumi Chumma Aadathu" meaning a Chozhiyan does not do anything without purpose. This group of Brahmins occupies mainly the villages of Kodunthirapally, Chembai, Nellayi, Padur and Vengassery.
The other interesting groups of Iyers found in Kerala are
the Mukkanis. They are the group of people who help the Potti
(Karnataka Brahmin) head priest to perform Pooja in
Thiruchendur Temple of Tamil Nadu. They say that during the invasion of Tamil Nadu by Malik Kafur, their forefathers who were the chief priests in Thiruchendur ran away and settled in a village called Mukkani. After the soldiers retreated they went back to claim their Pooja rights, they were told that due to their cowardly act they have lost this right. Most of them are settled around Trivandrum of Kerala.
There are then the Kurukkal who are a very small community doing Pooja in Shiva Temples owned and managed by Kerala Iyers in and around Palakkad. They are Shivacharyas and in the by gone era considered as inferior.
There are also Azhwars who are Bhattacharyas doing Pooja in Vishnu or Krishna Temples owned or managed by Palakkad Iyers. As mentioned earlier there is a considerable population of Iyers belonging to Krishna Yajurveda in Kerala. They perform Pratha Sandhya after the bath and again take bath before their Madyannikam. Because of this practice some people refer them as Madyanna Parayan.