You may be quite certain that it is the river which flows through Belfast. The song was first published in "Songs of Uladh" <> [Herbert Hughes and Joseph Campbell] published in Belfast by William Mullan and sons and in Dublin by MH Gill, 1904.

Hughes' preface says: "I made this collection while on holiday in North Dun-na-nGall in August of last year."
My Lagan Love is on page 32. The note says, "I got this from Proinseas mac Suibhne who played it for me on the fidil. He had it from his father Seaghan mac Suibhne, who learned it from a sapper working on the Ordnance Survey in Tearmann about fifty years ago. It was sung to a ballad called the "Belfast Maid," now forgotten in Cill-mac-nEnain." [This pretension in spelling etc is typical of the Gaelic Revival flavour of this book - it is also embellished with "Celtic knots" and fanciful derivations of half uncial script.]

There are four stanzas but sung as five with the repetition of the first one.

The second stanza, whose authenticity is thus placed beyond doubt is:

Her father sails a running-barge
'Twixt Leamh-beag and The Druim;
And on the lonely river-marge
She elears his hearth for him.
When she was only fairy-high
Her gentle mother died;
But dew-Love keeps her memory
Green on the Lagan side.

and the fourth:

Her welcome, like her love for me,
Is from her heart within:
Her warm kiss is felicity
That knows no taint of sin.
And, when I stir my foot to go,
'Tis leaving Love and light
To feel the wind of longing blow
From out the dark of night.

I don't have an idea what "elears" means, unless it's a misprint for clears but Lambeg is a village between Lisburn and Belfast and the Drum is the site of a bridge across the river and the canal which was made beside it which eventually diverged from the river and entered Lough Neagh.

There are notes on Leanan-sidhe "fairy mistress and on the crickets of the "crickets' singing stone" [note the apostrophe in "crickets'"] and these will help clear other mysteries made acute by distance. Except for the confusion over "dorring dooring, door-ring" - The book, our best authority in this case of a composed rather than traditionally constructed song, says "dooring" which I take to be a diminutive of "door" used for the sake of scansion!

Is that all?

HTML line breaks added. --JoeClone, 19-Nov-02.