Nia has multiple origins. In Swahili, it means "purpose" — one of the seven Kwanzaa principles. In Welsh, Nia is a name from medieval legend, said to mean "radiance" or "bright." In Irish, it is a variant of Niamh (also bright). The same syllable, three traditions.
Nia is rising in the U.S. and sits in the top 550.
Nia 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 Nia reduce to 6, The Nurturer. This is a traditional interpretive system, not a factual claim about the name.