The following is published in Seán McMahon,The Poolbeg Book of Irish Ballads. Dublin: Poolbeg, 1991. The second verse is similar to the Irish language verse "Is minic a bhréag tú mé ar do ghlúin, ..."
Seán's a man I don't meet everyday, but he doesn't live far from me, so maybe someday I'll question him about the source of this version. The words are very similar to a broadside version, Shula Agrah,published by Haly (19th century), which Bruce O. contributed to Mudcat 22 Sept 1999.

McMahon's notes:
"Eighteenth-century ballad associated with service in Europrean armies with residual Irish in the title and the first and last lines of the refrain. There are many versions since it is easily adaptable to particular places - the Brandon Hill named here is often changed. The title means literally, "Walk, love." and the almost buried [ie, corrupted] Irish of the last lines means, "May my darling travel safely."

SHUILE AGRA [note, stress the second syllable in Agra]
Anonymous

As I roved through my new garden bowers,
To gaze upon the fast fading flowers,
And think upon the happiest hours
That fled in the Summer's bloom.

chorus
Shuile, shuile, shuile agra,
Time alone can ease my woe;
Since the lad of my heart from me did go
Gotheen mavourneen slaun.

'Tis often I sat on my true-lover's knee
And many a fond story he told me.
He told me things that ne'er should be.
Gotheen mavourneen slaun.

I'll sell my rock, I'll sell my reel,
When flax is spun I'll sell my wheel,
To buy my love a sword of steel,
Gotheen mavourneen slaun.

I'll dye my petticoat, I'll die it red
And round the world I'll beg my bread,
That all my friends should wish me dead.
Gotheen mavourneen slaun.

I wish I were on Brandon Hill
'Tis there I'll sit and cry my fill,
That every tear would turn a mill
Gotheen mavourneen slaun.

No more am I that blooming maid
That used to rove the valley shade,
My youth and bloom are all decayed,
Gotheen mavourneen slaun.

Shuile, shuile, shuile agra,
Time alone can ease my woe;
Since the lad of my heart from me did go
Gotheen mavourneen slaun.

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I saw a 1995 message in IrTrad-L from Breandán Dalton in which he tells of Siúl a Rúin being sung in Scotland: "It was first made popular in Scotland during the Jacobite rebellion by Irish kerns fighting for Charles, and it gets a namecheck in [Robert Louis Stevenson's] novel 'The master of Ballintrae'."

Bruce O. also gives a Scottish version in this thread
Can anyone verify & quote The Master of Ballantrae citation?