Ruc language

Rục is a Vietic language spoken by the Ruc people of Tuyên Hóa district, Quảng Bình province, Vietnam. Rục literally means 'underground spring', and is a critically endangered language spoken by a small ethnic group that practiced a hunter-gatherer lifestyle until the late 20th century.

History
Ruc speakers were hunter-gatherers until the late 1970s, when they were relocated into sedentary villages by the Vietnamese government. The 1985 Soviet-Vietnamese Linguistic Expedition found that there were no more than 200 Ruc people. Half of the Ruc died from a cholera epidemic in the late 1980s. Today, the Ruc live together with the Sach in villages close to the Laotian border. Ruc settlements include Yên Hợp and Phú Minh.

Phonology
Unlike Vietnamese, Rục allows for presyllables with a minor vowel, such as cakuː4 'bear' (cf. Vietnamese gấu). Rục is notable for preserving many prefixes that have been lost in Vietnamese, including prefixes (such as *k.-) in archaic Chinese loanwords that are crucial for the reconstruction of Old Chinese