Manjusha is from the Sanskrit मञ्जूषा (Mañjūṣā — small box, jewelry box, treasure-chest). Manjusha is one of the Sanskrit feminine names — central to traditional Hindu heritage.
Manjusha 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 Manjusha reduce to 6, The Nurturer. This is a traditional interpretive system, not a factual claim about the name.