Celtic Myths on creation
Celtic mythology does not propose a single version or description of the creation as a whole, as other religions and mythologies do, but a few Celtic myths mention that heaven and earth was created by giants, considered by this peoples group to be the ancient original gods. According to another Celtic myth, the creation took place by the primordial, first god who, by means of a melody played by his breath, brought creation into existence.
The following passage is from a Celtic myth claiming that in the beginning nothing living existed—not even gods—but that the earth was comprised of land and sea.
Once upon a time, there was no time and that was when there also was no gods and no man walked the surface of the land. But there was the sea, and where the sea met the land, a mare was born, white and made of sea-foam. And her name was Eiocha.
Creation continues on. From an oak tree that grew in the land there sprouted a plant. This is where Eiocha gave birth to the first god Cernunnos. Cernunnos mated with Eioch and begot more gods; however, the gods felt lonely because they did not have anyone to command or to worship them, so from the wood of the oak tree they created the first man and woman, as well as other animals. Giants, too, are born from the bark of a tree that Eiocha hurled into the water.
Nothing more specific can be found, and as the exact origins of the stories above are not known, it is unclear whether they are original stories or latter inventions. As most Celtic myths were once only preserved orally, later Christian influences may have altered and distorted them.