Harshini is from the Sanskrit हर्षिणी (Harṣiṇī — joyful, full of bliss, delighting) — from Sanskrit harṣa (joy/bliss). Harshini is one of the Sanskrit feminine names — central to traditional Hindu heritage. BCE-2nd c.
Harshini 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 Harshini reduce to 5, The Seeker. This is a traditional interpretive system, not a factual claim about the name.