A written language:
The Celts did not have a written language until nearly the Middle Ages. Much of what we know about the Iron Age Celts comes to us from their oral legends and myths.
Celtic Written Language
Gifts the ancient Celts gave the world:
The invention of soap, Irish linen, Scottish plaids, Irish jigs, Scottish reels, Welsh dragons, the fiddle, the bagpipe, the Celtic harp, the longbow, and many wonderful folk and fairy tales.