Khmer Loeu
The indigenous ethnic groups of the mountains are known collectively as "Montagnards" or Khmer Loeu, a term meaning "Highland Khmer". They are descended from neolithic migrations of Mon–Khmer speakers via southern China and Austronesian speakers from insular Southeast Asia. Being isolated in the highlands, the various Khmer Loeu groups were not Indianized like their Khmer cousins and consequently are culturally distant from modern Khmers and often from each other, observing many pre-Indian-contact customs and beliefs. However, although diverse, they have many things in common. Most are matrileneal, tracing ancestry through maternal rather than paternal bloodlines. They grow rice and live in tribal villages.
Historically, as the Khmer Empire advanced, they were obliged to seek safety and independence in the highlands or become slaves and laborers for the empire. Zhou Daguan remarked that the Khmers had captured hilltribes and made them laborers referring to them as the Tchouang or slave caste. Tchouang, from the Pear word juang, means people. Presently, they form the majority in the sparsely populated provinces of Ratanakiri, Stung Treng, and Mondulkiri.
Their languages belong to two groups, Mon–Khmer and Austronesian. The Mon–Khmers are Samre, Phnong, Stieng, Kuy, Krung, and Tampuan. The Austronesians are Rhade and Jarai. Once thought to be a mixed group, the Austronesians have been heavily influenced by the Mon–Khmer tribes.
Read more about this topic: Ethnic Groups In Cambodia