Aleksandra is from the Macedonian / Polish / Russian Александра (Aleksandra) — Slavic rendition of Alexandra (Greek Aléxō defender + anēr/andros man) — defender of mankind. Aleksandra is one of the Macedonian + Polish + Russian + Serbian feminine names — central to traditional Slavic Orthodox + Catholic heritage.
Aleksandra 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 Aleksandra reduce to 5, The Seeker. This is a traditional interpretive system, not a factual claim about the name.