The English words for stone and Saxon are similar. One reads of how Arthur pulled the sword from the saxo, or the stone. Could this have originally read Saxon? Could the last letter have been smudged or just left off? Remember, the printing press hadn't been invented at the time of the writing of the first books to mention this curious how-Arthur-became-king story. One story would have been copied by a person into another book; that story would have, in turn, been copied by another person into another book; and so on. The possibility of an error in translation or even copying is frighteningly real. Arthur could very well have pulled the sword from the Saxon. This could have been his own sword, which he pulled from the body of the Saxon leader--symbolizing Arthur's great victory over the Saxons. The story could also have been of Arthur taking the sword from the dead body of a Saxon because Arthur's own sword had broken on the field of battle--an all too common fate for many weapons in the Dark Ages.
In the end, we just don't know. As with virtually all aspects of the Matter of Britain, we can't say for sure, from a historical viewpoint, what the truth is. We can't prove this point either way. Still, the possibility of an error in translation would be an explanation that a historian--someone used to dealing in facts and figures--could accept more easily than the fanciful tale of a lad coaxing a metal sword from a large anvil on top of a ton-weight stone.