The scholarly concensus of opinion is that Lord Hailes (James Dalrymple) simply (re)wrote the unique ballad 'Edward'. The 2 main reasons for this opinion are that at the time there was nothing else like it known, and the pseudo-archaic forced language it was couched in. Another lesser reason often quoted is the Scots would never have a song that used the despised name of 'The Hammer'.

The more likely scenario is that he cobbled it together from something else. There are older equivalents in Scandinavia and much has been written about those connections (Sir Halewyn by Grey, and others more recently). It is very likely that earlier versions existed in English under the radar, in both Scottish and English versions, but the possibility is also there that those versions that have turned up in oral tradition since 1900 derive either from the much printed 'Edward' or as translations from the Scandinavian. However, against the last idea is that all 3 variants in English more or less have the same components and are more closely related to each other than to the foreign variants with fuller stories. What would really help to focus the probabilities is that a version turns up at least as old 'Edward'.

If we were to propose the most likely scenario based on what happened with other Child Ballads in Scotland at that time, it would be Hailes or some other ballad hobbyist translated it from the Danish and that the other versions derive from that.

BUT, most of this is conjecture. As with many alleged 'fake' Child
Ballads, we don't actually know the real extent to which this happened. Many scholars have hinted that the fakery was rife, but with no hard and fast proof we mostly only have the ballads themselves to go on.