<Pedant> It's as much the double-d at the end, as the "i". "Dd" is a completely different letter to "d"; it's pronounced as a heavy "th" as in "this", "that", but not as in "throw". </pedant>

But I don't blame you for copying Welsh words or phrases from whatever source is available (even a plaque possibly manufactured in Taiwan, or wherever). I'd probably do the same with Greek, with equally glaring errors.

The Mudcat has plenty of Welsh speakers ready to give kindly advice, or pounce on solecisms.