Vishakha is from the Sanskrit विशाखा (Viśākhā — branched, having branches) — name of 16th nakshatra (lunar mansion). Vishakha is one of the Sanskrit feminine names — central to traditional Hindu + Buddhist heritage.
Vishakha 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 Vishakha reduce to 7, The Seeker. This is a traditional interpretive system, not a factual claim about the name.