It’s of a damsel both fair and handsome, Those lines are true as I’ve been told. On the banks of the Shannon in a lovely mansion Her parents claimed great stores a gold. Her hair was black as the raven's feather, Her form and features describe who can. But still a folly belong to nature, She fell in love with her servant man. Sweet Mary Ann with your love was walking When her cruel father drew quite near; And as those true lovers were fondly talking, It’s home in anger her father flew. To build a dungeon was his intention, To part those true lovers he concealed a plan. For he swore an oath that in reveal to mention That he’d part this fair one from her servant man. He built a dungeon of bricks and mortar, In flight a stair it was underground. And the food he gave her was bread and water, The only cheer for her was found. Three times a day he would cruelly beat her, Unto her father she thus began: ‘As I have transgraced you, now dear father, I’ll live and die with my servant man.’ Young Edward found out her inhabitation, It was well secured by an iron door; And in spite of all the nations He’d gain her freedom to rest no more. A toil at leisure, it was his pleasure, To gain relief for his Mary Ann. And he found his object and gained the treasure, She cried: ‘My faithful servant man.’ He brought for her a suit of clothes, Of men’s apparel for to disguise. Saying, ‘It’s for your sake, I would face your father, To see me here, it will give surprise.’ When her cruel father brought bread and water He called his daughter, she thus began: ‘Oh’, says Edward, ‘Enter, I’ll clear your daughter, And I shall suffer for your servant man.’ When her cruel father found out so tender, It was down he fell on the dungeon floor. He said, ‘True lovers shall ne’er be parted, Since love has forced through an iron door.’

“Found bearing the title ‘The Daughter in the Dungeon’, ‘The Cruel Father and the Affectionate Lover’ and ‘The Servant Man’, this song probably originated on the broadside presses in 19th century England where it was widely distributed. It also made its way to the United States and Canada in oral form; the writer of the note to a Vermont version identifies the earliest text as originating on a Catnach London broadside ‘prior to 1840’. As Paddy Tunney pointed out, the song has rarely been found among traditional singers in Ireland and printed versions have largely been confined to street ballads in collections such as O Lochlainn’s ‘More Irish Street Ballads’ and James N Healy’s ‘Irish Street Ballads’. Sam Henry gives one from County Tyrone entitled ‘Love Laughs at Locksmiths’, though he does not give a source. Tunney wrote in his note to the only other traditionally sung Irish version recorded outside of County Clare, from Tyrone singer, Francy Curry, ‘The King of Kilmassey’:

‘Then Francy sung us the complete version of a rare song seldom heard in Ireland, although (Peter) Kennedy infers in his ‘Folk Songs of Britain and Ireland’ that it must have originated in Ireland by reason of the fact that the young damsel's dwelling was by the banks of the Shannon. It has been collected in Sussex, Shropshire, Dorset, Hampshire, and Oxfordshire in England and in Nova Scotia and Newfoundland in Canada. In Ireland it was collected by Colm O'Lochlainn and Sam Henry. It is known by various names, such as ‘Her Serving Man’;’The Young Serving Man’; ‘The Daughter in the Dungeon’; ‘Love Laughs at Locksmiths’; ‘Since Love Can Enter an Iron Door’ and ‘The Cruel Father’. Where did Francy Curran, shepherd and songster who was never further from his native heath than Strabane in County Tyrone, get this song? The only conclusion I can come to is that he got it off a broadsheet at a rabble day in Letterkenny or Raphoe. These were the old hiring fairs where the planter farmers of the Lagan hired the sons and daughters of the native Irish in those infamous slave markets.’”
Jim Carroll

Reference:
Where Songs Do Thunder, Paddy Tunney, Appletree Press 1991.
Songs of the People, Sam Henry, Univ. of Georgia Press, 1990.

See also
The Iron Door sung by Katie Droney