Branwen combines the Welsh bran (raven) and gwen (white, fair) — meaning "white raven." Branwen is one of the principal heroines of the medieval Welsh Mabinogion, daughter of Llŷr and sister of Bran the Blessed.
Branwen is widely used in modern Wales.
Branwen 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 Branwen reduce to 5, The Seeker. This is a traditional interpretive system, not a factual claim about the name.