Nyx (Νύξ) is the Greek goddess and personification of night — one of the primordial deities, mother of many gods including Hypnos (sleep), Thanatos (death), and Hemera (day).
Nyx is rare as a given name but rising — chosen for its mythological weight and modern sound.
Nyx 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 Nyx reduce to 9, The Giver. This is a traditional interpretive system, not a factual claim about the name.