Perhaps from Mongolic, compare Mongolian нүүр (nüür, “face”).
ньуур • (nyuur)
- (anatomy) face, countenance
- (sur)face (of an object, especially the top or front side)
- остуол ыраас ньуура ― ostuol ıraas nyuura ― the clean surface of a table
- (geometry) face
- сирэй (sirey, “face (anatomy, geometry)”)