Bronwyn is a Welsh name from bron (breast) and gwyn (white, fair, blessed) — meaning "fair-breasted" or "white-bosomed." The Welsh spelling Bronwen (with E) is the traditional female form; Bronwyn (with Y) is the more common Anglicised spelling.
In Welsh mythology, Branwen (a related but distinct name) is one of the central figures of the medieval Welsh tale The Mabinogion — a princess whose marriage to the Irish king causes a war between Ireland and Wales.
Bronwyn 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.
In Pythagorean numerology the letters of Bronwyn reduce to 3, The Communicator. This is a traditional interpretive system, not a factual claim about the name.