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 reduces to nine — the number of legendary grace.