Charlie is the English diminutive of Charles — from the Old Germanic karl ("free man, peasant"). Charlie's sister Sally also features. Princess Charlie is Princess Charlotte of Wales's nickname. Charlie Hunnam is male.
Charlie 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 Charlie reduce to 2, The Peacemaker. This is a traditional interpretive system, not a factual claim about the name.