Board Thread:Questions and Answers/@comment-88.171.110.213-20150322210405/@comment-1173941-20150322213022

"Original Sword Skills" are sword skills you create.

It actually hasn't shown us Kirito using any Original Sword Skills at all. It was explained in some extra content that Kirito could recreate some of his Dual Blade abilities, but the details aren't really explained in the story.