Lieu is from the Vietnamese Liễu (柳 — willow). Liễu Hạnh Princess is one of the Four Immortals of Vietnamese folk religion + mother goddess of the Đạo Mẫu (Mother Goddess) religion of Vietnam — venerated at Phủ Dầy Temple Nam Định (UNESCO Intangible Heritage 2016 for the Practices Related to Vietnamese Beliefs in the Mother Goddesses of Three Realms).
Lieu 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 Lieu reduce to 2, The Peacemaker. This is a traditional interpretive system, not a factual claim about the name.