Uh, as much as I enjoy The Pogues, they are not exactly what I would call sticklers for tradition -- and I certainly don't think they claim to be. They often play fast and loose with accepted traditional lyrics to make a point, fit an arrangement or just plain because they feel like it (or maybe even don't know any better).

The folk process DOES work its way on traditional words whether because the singer heard it wrong to begin with or the brain somehow segues into the "new" words after singing it for awhile. Best advice is to sing what makes sense, be aware of various versions and know WHY you sing it the way you do. First rule is check the source singer -- especially if there is only one collected version. Don't change anything that you wouldn't want to be the only source left for a future collector/historian.

Bat Goddess