Lavender is from the Latin lavare ("to wash") — Romans bathed in lavender-scented water. Lavender also denotes a pale purple color and, since the late 19th century, has been a symbol of lesbian and gay identity — Sappho was associated with violets, and "lavender" became coded slang in 19th-century America. Lavender Brown is a character in J. K.
Lavender 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 Lavender reduce to 9, The Giver. This is a traditional interpretive system, not a factual claim about the name.