Well, I learned the song from Tommy Maken's singing and I always sang "diamond" not "demon".
There's a fiddle and banjo player in these parts named Dermy Diamond, a gem (and that's how his surname is pronounced)

The usual verses are given in Bunting. "It is pretty to be in Ballinderry ...under an Ivy tree...
Oh! that I was in little Ram's Island ...with Phelimy Dialmond...we would make the whole Island ring." Edward Bunting published his work in 1840, but I am looking at D. O'Sullivan & M. Ó Súilleabháin's edition of "Bunting's Ancient Music of Ireland", Cork University Press, 1983; which is based on Bunting's original manuscripts.

"Both air and words were collected from Dr Crawford of Lisburn, in 1808. Another version of the words, from Mrs. Houston, was p[rinted in the Jpurnal of the Irish Folk song Society, vol. V (1907), p.37. It runs as follows:

O, it's purty to be in the bonny Church Island,
Nobody there but Phelim my diamond;
Phelim would whistle and I would sing, Until we would make Church Island to ring.

Phelimy, Phelimy, why did you leave me?
Sure I could bake, I could sew, I could spin.
Phelimy, Phelimy, why did you leave me?
I'll tell the priest on you Phelimy, Phil.

O. lonely I wander on bonny Church Island
Far, far away from Phelimy diamond
The birds may whistle a merry tune,
But sorrowful May brought woeful June.

Och, cold in the ground my Phelim's lying,
Over his grave I am sobbing, I'm sighing
To leave him his love would be a sin,
So take off the sod and lay me in."