as there is more than one set of lyrics to Boyne Water, I refer anyone interested to this background information
http://www.fresnostate.edu/folklore/ballads/PGa015.htm
though I wonder why the older Ros Catha na Mumhan isn't mentioned as a source for the tune

The Session gives the chords G, Am and Em; scroll to the third setting at https://thesession.org/tunes/2569

And here are the lyrics and info re Lady Keith's Lament from Connie Dover's album, "If Ever I Returned"

“Lady Keith’s Lament” was published in 1819 in James Hogg’s collection, The Jacobite Relics of Scotland, being the Songs, Airs and Legends of the House of Stuart, and appeared under the title “When the King Comes O’er the Water.” The Jacobites were partisans of Scotland’s ruling family, the Stuarts, who, by 1603 sat on both the English and Scottish thrones, and who were ultimately deposed. This song was either composed by or written in behalf of the daughter of the Earl of Perth, whose maiden name was Lady Mary Drummond, and who was strongly attached to the Stuart clan. That she looks for her king’s return and her country’s salvation with the eager anticipation of a bride awaiting her groom is typical of the romantic view many Scots held of the exiled Stuart kings.

LADY KEITH’S LAMENT LYRICS, Traditional Scottish
From the CD, If Ever I Return:

I may sit in my wee old house at the spinning wheel to toil so dreary
I may think on a day that is gone, and sigh and sob till I grow weary
I ne’er could brook, I ne’er could brook a for-eign king to own or flat-ter
And I will sing a ranting song the day our King comes o’er the water

I have seen the good old day, the day of pride and chieftain’s glory
When royal Stuart held the sway and none heard tell of Whig or Tory
Though silver be my hair one day, and age has struck me down, what matter
I’ll dance and sing that happy day, the day our King comes o’er the water

If I live to see the day that I have begged and begged from heaven
I’ll fling my rock and reel away, and dance and sing from morn till evening
For there is One I will not name who comes the beingin bike to scatter
And I’ll put on my bridal gown the day our King comes o’er the water

A curse on dull and drawling Whig, the whining, ranting, low deceiver
With heart so black and lies so big, the canting tongue of clishmaclaver
My father was a good lord’s son, my mother was an earl’s daughter
And I’ll be Lady Keith again, the day our King comes o’er the water