Lena, The song is called " In A Shady Nook One Moonlight Night". The following is all I can remember, I am not even sure if there is any more, but I'll check and resubmit unless someone else comes up with additional verses ?. It concerns the legend that if you catch a leprauchan he will lead you to a pot of gold, he cannot escape as long as you keep your eyes on him. If you look away even for an instant he will be gone.

In a shady nook one moonlight night
A leprauchan I spied
With scarlet coat and cap of green
A cruisceen by his side
Tick Tack Tick his hammer went
Upon a lady's shoe
Oh I laughed to think of a pot of gold
But the fairy was laughing too

With tip toe step I seized the elf
The fairy purse I cried
The purse he said is in her hand
That lady by your side
I turned to look and the elf was gone
Oh what was I to do
Sure I laughed to think what a fool I'd been
And the fairy was laughing too