Thampi

The Thampis are the sons of the Maharajahs of Travancore and their morganatic wives belonging to Illathu Nair or other similar Kshatriya castes. They form a part of the Nair caste (even if the mother is a non-Nair, as in the case of the Kunju Thampies) and had no title of succession to the throne.

Origin

Since the Maharajahs of South Kerala (Travancore) also belong to the warrior race of the Nairs, they followed the matrilineal system (Marumakkathayam) of inheritance. Hence when a king died his sister's son would become the next Varma (Samantha Kshatriya) ruler and his own son born of his wife, usually of the Illathu Nair caste would be called Thampi with the title "Kannaku Chempakaraman" which was also one of the highest titles of nobility in Travancore.

All of the Maharajahs' female descendants were known by the style of Kochamma or Thankachi added to their name. The sons, as mentioned, were styled Thampis with the title of Kanakku Chempakaraman. Since the Marumakkathayam law of matrilineal inheritance existed in Travancore, the sons of these Thampi gentlemen would, however, not gain any distinguishing title.

Families from where Maharajas got married are known as "Ammaveedus". Arumana Ammaveedu, Vadasseri Ammaveedu, Nagercoil Ammaveedu, Thiruvattar Ammaveedu, etc. are some of the prominent families in Trivandrum from where the Maharajas of Travancore married. The Rajahs of Travancore traditionally took wives from Ammaveedus and such Royal consorts, known as Ammachis would get the additional title of Panapillai Amma. If at all another lady from outside the Ammaveedu's was to be married to the Rajah, she would be adopted to one of the Ammaveedus first and then wed to the King. This was the case in the marriage of Maharajah Swathi Thirunal, Maharajah Ayilyam Thirunal and Maharajah Moolam Thirunal.

Unnithan

Unnithan (Malayalam: ഉണ്ണിത്താന്‍) is the modern form of the older title of Thankal (താങ്കള്‍). Unnithans were among the highest of the Nair aristocracy in the Travancore region of the Indian state of Kerala. Unnithan ladies (Kunjammas) of the Edassery Pattaveettil family were often married by the Rajahs or princes of the royal families such as Mavelikara, Ennakad, Prayikkara etc. They are mostly of Central Travancore origin.
Unnithans were never addressed in gatherings by their first names but instead by their family names with the title of Eman (ഏമാന്‍, a corruption of Lord),and as Thankal, even by the Maharajahs. Their women used the honorific title of Kunjamma, indicative of their greater status among the Nair community, where ladies unanimously used the title of Amma.
While other titles of nobility were used by members of various castes such as Panicker, Pillai, etc., Unnithan or Thankal was a title of high status reserved only for the highest class among the Nair aristocracy. All Unnithans were, in the past, addressed formally only as Thankal while the later term was a general surname.
These classes of Nairs dominated the civil, administrative and military elite of the Pre-British era in Kerala.The ban on their kalaris and personal army by the British along with the Land reforms in early 1900s and 1950s which lead to massive loss of land-ownership was a major blow to their social standing and power. However, they continued to be feudal Land-lords, and still owned large estates, till the Land Reforms Ordinance, which set a ceiling on the land holdings that a person or family could possess was enacted by the Kerala State Government which was the first communist state government popularly elected to power in India, which reduced many of these families to poverty overnight

Rajput is a caste or Jati and so is Nair

What above written is false.
Rajput is a caste or Jati and so is Nair.
Caste status and role of Nair and Rajput is identical.
Both served as warrior aristocracy.
Robert Orme had described Nairs as prouder and even haughtier than Rajputs (Note that he chose Rajput to compare)
Asiatic Journal of 1828 edition also note that Nairs physically resemble Rajputs the most.
It is a lie that Nairs collaborated with British and Portuguese. In fact even a glance at text books prescribed for BA history students should prove the point.
Nairs fought relentlessly and savagely all those who invaded Kerala, and in course of time pushed back all invaders - Kalabhras, Kadambas, Cholas, Portuguese, Dutch, Mysore Nawabs. Only invader who had decisively defeated Nairs are British - and they did it more by trickery than force - blame for which must go on Rajas rather than on Nairs as a caste.
Above mentioned post only take into consideration of Nairs of South Kerala but no mention is made of heroic struggle waged by Nairs of Malabar or North Kerala on Hyder Ali and Tipu Sultan for twenty years in form of guerrilla warfare and bled Hyder and Tipu dry and weakened them during their wars with British enemy.
There is also no mention about 14 year long Cotiote War waged between a Nair oriented force of Kerala Varma Pazhassi Raja and British armies. Cotiote War is one of the longest and bloodiest war waged by British in India.