Miki is from the Japanese 美貴 / 美樹 (Miki — mi beautiful + ki princess / tree) Greenlandic miki (small, little). Miki is one of the Japanese + Greenlandic feminine names — central to traditional Japanese heritage.
Miki 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 Miki reduce to 6, The Nurturer. This is a traditional interpretive system, not a factual claim about the name.