Lü (呂) is the surname of Empress Lü Zhi (241-180 BCE) — wife of Liu Bang, founder of the Han Dynasty, and the first formally recognized empress in Chinese imperial history. Notoriously ruthless, she had Liu Bang's favorite concubine Lady Qi mutilated and turned into a "human pig."
Lü 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 Lü reduce to 6, The Nurturer. This is a traditional interpretive system, not a factual claim about the name.