If you date the link from the 1840s/1850s the Liverpool singer of the song would surely know it was based on an Irish song of his or his father's generation. Would the Liverpool sailor have passed on the song without revealing it's roots? Would he have known it's roots? How well known was the Limerick song? If anyone can date the Limerick song to the 1840s/1850s period or before then that would make me start thinking that the Limerick song came before the Liverpool song.

MV