Cindy is the English diminutive of Cynthia — from the Greek Kynthia ("from Mount Kynthos" on Delos, the birthplace of Artemis).
Subject of countless 1990s fashion histories.
Cindy 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 Cindy reduce to 1, The Leader. This is a traditional interpretive system, not a factual claim about the name.