These lines appear in a lot of old murder songs. I would guess that "Delia" is older than "White House Blues" but not by much. McKinley was assassinated in 1901 and the song couldn't be too much younger. By the time Charlie Poole recorded it in the 20's it had some verses which were less than respectful. In any case Renbourn's version doesn't sound like either "Delia" or Charlie Poole's "WHB"