If it's actually old, the song may have been meant as a teaching song. It says 'look what can happen if you go off with a stranger.'

In the late middle ages, there was a social problem where certain men traveled the countryside, marrying and abandoning one woman after another. Picture a young woman without no eduction, who's never been more than three miles from home. Where would she learn to be suspicious of a confidence man?

This kind of song may stand between that era and the era of Pretty Peggy, who lowers her eyelids demurely and tells Captain Willie to get lost, declining to wind up among the camp followers when he's tired of her.