Exactly so, Malcolm. And this is why I cautioned against taking the words of any one ballad version as some sort of gospel.
One of many examples of how ballad lyrics get altered can be found in The Golden Vanity (or any of the various titles by which it is known). Leaving out whether boring a hole in the side of a ship while treading water is even possible (the subject of much argument in a previous thread), in the version I learned from a record by Richard Dyer-Bennet, the line is "And with his brace and auger, in her side he bored holes three." In some American mountain versions, the line is "He had a little tool all fit for the use, and he bored nine holes in her hull all at once." The singer may not have known what a brace and auger was, so he or she just did the best they could. That's one of the many ways the oral tradition alters folk songs.
It would be pretty fruitless to wander through your local hardware store or dig through old technical manuals trying to find some tool that could "bore nine holes all at once." "Pocket knife" is obviously some fairly recent addition to Matty Groves/