The symbol Au is from the Latin: aurum, the Latin word for "gold". The Proto-Indo-European ancestor of aurum was *h₂é-h₂us-o-, meaning "glow". This word is derived from the same root (Proto-Indo-European *h₂u̯es- "to dawn") as *h₂éu̯sōs, the ancestor of the Latin word Aurora, "dawn".
This etymological relationship is presumably behind the frequent claim in scientific publications that aurum meant "shining dawn".