Hadley is an Old English place name and surname — from hǣð (heather) and lēah (clearing, meadow). The original sense is a meadow covered in heather. The name appears in English records from the medieval period as a surname.
Hadley has been used as a first name since the 2000s, particularly in the U.S., where it now sits in the top 120. The actress Daisy Ridley's character in the Star Wars films is not Hadley — but the name belongs to the same modern wave of surname-as-first-name choices.
Hadley 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.
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In Pythagorean numerology the letters of Hadley reduce to 1, The Leader. This is a traditional interpretive system, not a factual claim about the name.