The present Nepalese nation is a combination of two big races of the Himalayan country of Nepal who are known by the name of Kirat and Khas tribes. In the beginning, the Kirat tribes had occupied all the countries of the Himalayan mountains extending from Afghanistan to Assam and North Burma. Later on the Khas tribe came from the North and fought with the Kirat people and distributed the Himalayan countries into two big divisions. The land between Kashmir to river Trisuli was called Khas land and the residents were called Khasiyas or Khasis or Khas people. The land between river Trisuli and Assam was called the Kirat land and the people were called Kiratese or Kirat people. They were ally tribes from the time of Mahabharata. Both the tribes had represented their armies in the battle of Kuruchetra. During 317 BC, both tribes had jointly helped King Chandra Gupta against his enemy Nanda King of Magadha.
The Khas had many languages with a few dialects; the Kirat had also many languages with various dialects.
In the beginning the Vedic Aryans had no acquaintance with both the Kirat and Khas people. The latter also did not care to know about and study their culture. So the Vedic Aryans composed a poem in Sanskrit about the Kirat and Khas tribes ignoring them from their fold. They have called them, "Shudras" or foreigners.
"Shanakaistu kriye loped imah kshatriya jatayah, Brikhalatwam gata lokey Brahmana darshanena cha, Paudra Kaschou Dravidra Kamboja Yauwanah Sakah, Parada Palhawa Chinah Kiratah Daradah Khasah."
Although the tribes called Tangan, Kulinda and Daradas were separate from the Khas tribes, Rahul Sankrityayan proves that they belonged to the same Khas people of the Punjab hills. The original habitat of the Khas tribe was on the basin of river Tarim in Central Asia. Their fort was called the Khas garh. When they were disturbed by a nomadic tribe called Laghu Uichi Kushan, they left their native land and migrated towards the Himalayan countries of Chitral, Gilgit, Kashmir, Kulu, Punjab hills or Kumaon, Garhwal and Nepal. The Tibetans had already known them by the name of Horpa with their ally tribe called Sokpa or Mongolian.When they intermingled with them, they were called the Horsok tribe. As the Horpa tribes were of bigger built and their faces were comparatively bigger than that of the Tibetan people, they called them Khachhe Khas tribe which means the Khas tribe of people who had bigger faces.
The Chinese people also remarked the Horsok or Khachhe Khas tribe to be of white colour, blue eyes, sharp noses and grey hair. They are not actually Aryans, but either Turks or Mongolians. Many people make a mistake of thinking Turks to be Muhammadans. But in fact, a Turk means the Western Mongolians who were descendents of the Tyurk of Japhetist race of the Western direction228, and Khan was their leader. The word Gurkhan means the King of Kings in their language. The word ourkha of Nepal appears to have been derived from the Gurkhan of Central Asia. The famous Gurkhan of Khas people in Tarim land was Yelu whose scion ruled there for three generations after which this Gurkhan dynasty was ousted by the enemies from there. So these Khas tribes with their Gurkhan left their native place and came towards the Himalayan countries of Chitral, Gilgit, Kashmir, Ladak, Kumaon, Kulu, Garhwal and Nepal and settled there permanently. Thus, those Khas people of Chiral and Gillgit called themselves to be of Kho tribe; the same Khasas of Kashmir and Ladaks were called Khachhey tribe. In the Kumaon province they called themselves Darad, Kunet or Kuninda and Tangan tribes. In Garhwal they were called Khasas or Monpas or Bhotias, though they are now proud of calling themselves Rajput Hindus. And in Nepal they are called Khas or Kshetri tribe.
As I mentioned before, they had to encounter the Kirat people in all the above mentioned places in the beginning, but later on came to good terms with them and mixed with them and constituted a big race. When a good relationship was made among them, they divided the Himalayan region into two big divisions; the Eastern and the Western Himalayas. The Kirat people ruled the Eastern Himalayas and the Khas people ruled the Western Himalayas. River Trisuli was the boundary between these two divisions. In this way, the land between river Trisuli and Kashmir was called the Khas land and the land between river Trisuli and Assam was called the Kirat land. Gradually the Khas tribe and Kirat tribe mixed so much so that they began to claim the same family title for both tribes. For example, the family titles of Kharka, Thapa, Rana, Punwar, Konwar, Gharti Burathoki, Baral, Rimal, Rijal, Darlami, Khulal, Sinjali, Basnet, Karki, Bohora, Bista, Singh and Sen can be found in both Khas and Kirat tribes. The practice of Feudalism was common in both tribes and the system of election for common overlordship was also famous among them. Thus, a league of Barah Thakuris ruled Jumla. A league of Barah Magar tribes ruled Mangrat. The Char Ghaley tribes ruled Lamjong. The Nau Gurungs tribes ruled Pokhara. The Ath Khas tribes ruled the Gorkha estates in West Nepal. The Naulakh Kirat ruled Majhkirat and Tem Limbus ruled the Pallo Kirat or Limbuwan in East Nepal.
The famous eight Khas tribes that I found in my MSS are Thapa, Bohora, Karki, Basnet, Rahut, Roka, Bista and Kharka in which Kharka was their Gurkhan or King and Bista was their priest. So long they were not converted into Hinduism, they had free matrimonial connection with the Kirat people of Magar tribe and so they had common family titles. But since the time of Khas people's conversion into Hinduism, they began to feel themselves high caste Hindus and so they themselves separated from their neighbors. They adopted the Devnagri script for Khas language and administered their lands. But since the time of Gorkha King Prithvi Narayan Shah all the Khas Kingdoms as well as Kirat Kingdoms were brought into one unity with common name of Gorkhas. So, the old feeling of relationship between the Kirat and Khas families began to revive and the national feeling grew stronger and the country of Nepal started adopting one language, one literature and one national name of brave Gurkhas alias Nepalese nation.
During 1845-46 AD, the Nepal Government formed a regiment of 6000 Kirat soldiers of Limbuwan in the Nepalese Army and stationed them in Patan with the name of Bhairab Nath.
In the year 1889, the Nepal Government permitted the British Government to form a Battalion of Kirat soldiers under the title of Gurkha Rifles. So they raised a Battalion and called it the 10th Gurkha Rifles. In the same manner in 1907, a 2nd Battalion of Kirat soldiers was formed and called it the 7th Gurkha Rifles.
Thus, the Khas Kirat tribes of Nepal became the world famous Gurkhas alias Nepalese nation.
Source: Kirat M.M.S. and Kirat itihaas by iman sing chemjong.