Those English lines in the 4th verse are in a song that A. L. Lloyd in Folk Song in England lists in his index as "The Water is Wide", although he neglects to give a title to the song on the page where to song is given. It's another conglomeration, and the verse in question belongs more properly to a song usually called "I'm a rover".

What is the age of the Gaelic text that Philippa gives? No documentation usually means there's real no basis for claiming any old origin for the song. John Moulden still has by far the most facts that I can see, and I've found that's almost always the case. Few can compete with him when it comes to history of Irish Songs.