There is no direct translation of "Edda" in Welsh. If you're looking for a Welsh equivalent, it would depend on what you want to convey.
For example, if you're talking about the "Poetic Edda," you could use a phrase like:
* "Casgliad o gerddi Norseg" (Collection of Norse poems)
If you're referring to the "Prose Edda," you could say:
* "Casgliad o straeon Norseg" (Collection of Norse stories)
Let me know if you have more context, and I can help you find a more precise Welsh translation.