Kenneth is a traditional Scots name. I believe there was a King Kenneth in medieval times. Eleanor is more of a Norman name, as in Lord Thomas and Fair Eleanor, Queen Eleanor's Confession. Professor Scott who sent him the trad version from his maidservant, will no doubt be found by Googling. As you know there are several Scotts involved in ballad collecting/editing. It would put the ballad back to the middle of the 18thc at least if what Jamieson says is right, but we already had a good idea it was at least that old anyway. Don't know anything of an RJ jr.

Jamie Warwick. In a foreign country names are easily transposed. Jamie seems to be a common occurrence in the ballad, albeit Jamie Randall.

Just for the record, I quite like Jamieson's ballad. Unfortunately the penultimate stanza looks like something out one of Sam Cowell's burlesques.