From Welsh gwyn meaning 'white, fair, blessed,' borne by figures in Welsh mythology.
Gwynn derives from the Welsh adjective gwyn, meaning white, fair, or blessed — one of the foundational color words in the Welsh language, carrying connotations not merely of physical whiteness but of purity, holiness, and good fortune. It is the masculine form; the feminine is gwen, familiar in names like Gwen, Gwenllian, and Guinevere (itself a Welsh compound meaning white phantom or fair and smooth). Together, gwyn and gwen form one of the most productive roots in Welsh nomenclature, generating dozens of names across fifteen centuries of recorded usage.
In Welsh mythology, the most prominent bearer is Gwyn ap Nudd — Gwyn, son of Nudd — who rules Annwn, the Welsh Otherworld, and leads the spectral Wild Hunt across the winter sky. He is a figure of tremendous, unsettling power in the Mabinogion and related texts: a king of the Tylwyth Teg (the fairy folk), the custodian of the souls of the dead, and an annual combatant with the warrior Gwythyr ap Greidawl for the love of Creiddylad — a battle decreed to continue until Doomsday. Gwyn ap Nudd's name encodes the paradox of the Otherworld itself: fair and white, yet master of death and the midnight hunt.
As a modern given name, Gwynn occupies a gentle revival in Welsh-speaking communities and among those with Welsh heritage who want a name authentically rooted in the Celtic linguistic tradition. The double-n spelling signals Welsh orthographic conventions to the knowing eye and distinguishes it from the surname Gwynne familiar in Anglo-Welsh contexts. It works as both a given name and a middle name with quiet elegance, short and melodic, requiring no explanation of its beauty while rewarding those who know its mythological depths.