Mayu is from the Quechua mayu — river + Japanese 真結 (Mayu — true bond / cocoon). Mayu is one of the Quechua feminine names — central to traditional Inca + Andean Indigenous heritage.
Mayu 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 Mayu reduce to 6, The Nurturer. This is a traditional interpretive system, not a factual claim about the name.