Possibly from Hebrew meaning bronze, or an Old English place-derived name.
Arda occupies a fascinating position in the landscape of given names, carrying resonances from multiple entirely distinct traditions. R. Tolkien's legendarium, Arda is the Quenya name for the entire world — the Earth itself as created by the Valar at Ilúvatar's command — making it one of the most cosmically significant names in modern mythopoetic literature.
For readers of The Silmarillion, the name evokes the whole of a carefully constructed mythological cosmos, a world shaped by music before it was shaped by matter. That association gives Arda an extraordinary depth for a name of only four letters. Independently of Tolkien, Arda functions as a given name in Turkish culture, where it is used for both boys and girls and carries connotations of purity and greatness — to "walk with the greatness of one's ancestors" is one interpretation offered in Turkish naming traditions.
The name also has Armenian usage, appearing as a given name and a place name (Artashat, historically significant in ancient Armenia). In each of these traditions, Arda carries a quality of weight and distinction rather than delicacy. The name has been quietly gaining attention among parents drawn to Tolkien's world — a subtler choice than Arwen or Legolas, carrying the mythology's grandeur without its more obvious signals.
It also appeals to those with Turkish or Armenian heritage seeking a name that travels well across linguistic boundaries. In any context, it is brief, strong, and genuinely unusual — a name that invites questions and rewards the explaining.