Samui is from the Japanese samui (寒い — cold). Samui is a character in Masashi Kishimoto's Naruto: Shippuden — a Cloud Village (Kumogakure) Jonin and leader of Team Samui, comprising her younger brother Atsui, Karui, and Omoi.
Samui 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.
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In Pythagorean numerology the letters of Samui reduce to 9, The Giver. This is a traditional interpretive system, not a factual claim about the name.