User blog comment:Laquearius/Cú Chulainn vs Fionn mac Cumhaill/@comment-422690-20170711151040/@comment-422690-20170711173446

I don't have an exact source, however most of what I have found/read points toward Claidheamh Soluis and Cruaidin Catutchenn being the same sword, or at least very, very similar. Claidheamh Soluis, meaning "Shining Blade" or the like, does release light; that much should be obvious from the name.

A quick search for a more specific source gave me O'Rahilly's Early Irish History and Mythology as the most prominent scholarly source indicating this.