Rebel is from the Old French rebelle / Latin rebellis (warring back, defiant) — a modern American word-name in the rebellious-spirit aesthetic. A top-1000 US baby name since 2018.
Rebel 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 Rebel reduce to 6, The Nurturer. This is a traditional interpretive system, not a factual claim about the name.