Oyuun is from the Mongolian Оюун (Oyuun — wisdom, intellect, mind). Oyuun is one of the Mongolian feminine names — central to traditional Mongolian Buddhist + Tengrist heritage. PhD Cambridge geochemistry.
Oyuun does not currently appear in the US Social Security Administration's top 1,000 girls' names, so we don't publish a US rank or birth count for it. That says nothing about the name's standing elsewhere in the world — only that it sits outside the ranked US data we rely on.
In Pythagorean numerology the letters of Oyuun reduce to 6, The Nurturer. This is a traditional interpretive system, not a factual claim about the name.