Here's my try at a transcription of what the Fureys sing (the very few changes from Maryrrf's in bold for comparison). I had two further copies of the lyrics of that song to help me with the job.

Does anyone know about where it comes from?

Wolfgang

MCSHANE

1. My name is McShane from the plains of Kildare.
A farmer I was until the last year,
Till I took a notion of higher promotion,
Went over to England the harvest to share.

Chorus: Room Toora La, Room Toora Laddie,
Room Toora La Mush a room toralay

2. I parted with Molly so blythe and so jolly,
Picked up a stick for a staff in me hands,
And to keep meself cheery for fear I'd get weary,
I sang Paddywhack as I went on my way.

3. I landed at Dumbarton on a fine summers evening.
Me bundle and staff I held them in me hands.
There were some of them laughin' and some of them chaffin',
More of them trying to stick Paddy away.

4. I went into a woman to ask her for lodgin's.
She said: "Me young man, now don't look so dull!
For I will tell you where you will get lodgin's
With a woman that lives next door to The Black Bull."

5. So I went to this woman and asked her for lodgin's.
She instantly showed me to a bed in the room,
And I being so tired and worn out from walkin',
I threw meself down in me bed in the room.

6. But a lump of a Tinker lay up in the corner.
He swore 'pon his soul sure he'd kill all was there.
Says I: "Me bold Tinker, give over your braggin'.
I'm bold McShane from the plains of Kildare!"

7. But he tried for to hit me a punch in the stomach.
I instantly fetched him a one in the throat,
And he tumbled heels over his head in the corner
And put all his head in an old rusty pot.

8. He lay on the floor; like a sheep he was bleedin'.
I swore 'pon my soul sure I'd cut off his life,
But I lifted him up and sent down for a noggin.
Me and the Tinker we ended the strife.

REPEAT FIRST VERSE.