Folklore often attaches events to noteworthy (real or mythical) individuals. There's an example in the DT link posted by (the late lamented) Malcolm Douglas:
"Edmund Ryan of the Hill was an Irish earl displaced by Cromwell after the Battle of the Boyne".

Even for Cromwell that would have been a remarkable achievement, considering that by then he had been dead for more than 30 years.

And the tune on that page is significantly different from the one that I'm familiar with from recordings of at least two singers.