This is a knotwork design that transmogrifies itself into an image of An Claidhheam Soluis, or "The Sword of Light". Parts of it are pretty representational, but other parts - notably the hilt - are really abstract knotwork patterns in the shape of the object.
An Claidheamh Soluis itself was certainly the name of a bilingual Irish / English newspaper in the early 20th century, a part of the Celtic Revival movement; it just as certainly was the name of an fictional sword in Padraic Colum’s wonderful book The King of Ireland’s Son. But while some will tell you that it was the traditional name for a legendary sword, I’m almost positive that it wasn’t.
It just sounds that way, especially to anyone who doesn’t know that actual legendary Irish swords had names that were a little less metaphysical - like "Retaliator", or "Swift to Hand".
In the true Irish stories no one ever noticed if there was some kind of misty Celtic twilight going on; because limbs and heads were flying every which way, and at times like that you’ve got to pay some pretty serious attention.
Anyway the paper was a great thing, the Padraic Colum book was a great thing, and here I’ve made of it a thing of my own.