Shu (淑) is the Mandarin Chinese word for "kind," "gentle," or "virtuous" — the classical Confucian feminine virtue.
Shu is widely used in China and Taiwan.
Shu 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 Shu reduce to 3, The Communicator. This is a traditional interpretive system, not a factual claim about the name.