Caroline is the feminine of Charles — ultimately from the Old Germanic karl, meaning "free man" (in the sense of "not enslaved").
Caroline has been continuously in the U.S. top 200 for over a century. Queen Caroline of Ansbach (consort of George II) and Princess Caroline of Monaco are well-known bearers. Today it sits in the U.S. top 90.
Caroline 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 Caroline reduce to 5, The Seeker. This is a traditional interpretive system, not a factual claim about the name.