It appears to have started life as a poem:

Found here:

"The Heathery Hill" by Ethna Carbery [aka Mrs. Seumus MacManus, Anna Johnston] (1866-1902)
From: The Four Winds of Eirinn: Poems by Ethna Carbery. (Anna MacManus.), Complete Edition, Edited by Seumas MacManus. Dublin, Ireland: M. H. Gill and Son, Ltd. 1906. p. 26.

Editor: Mary Mark Ockerbloom


THE HEATHERY HILL.

I MIND it well, and I see it yet
In a halo of sunset glory,
When I climbed knee-deep through the gorse and fern
To keep my tryst with Rory.
Like a singing-flame the little red lark
Poured the joy of its heart above me;
My grief, my grief! for the Heathery Hill
And the lad that used to love me.

The blue mist eerily drifted down,
Till the kine were lost in shadow,
'Twas time for Rory to come this way
By boreen and dewy meadow.
Then, then a song, that was sweeter far
Than thrush's or lark's, rose near me–
Oh! I'm thinking long for the Heathery Hill
And the voice of my lad to cheer me.

I miss my mother the livelong day–
Sure I was my mother's treasure;
I cry in dreams for my father's fields,
And the city holds no pleasure:
I'd part its ease and its golden store,
Though the wise folk may deride me,
For a summer eve on the Heathery Hill
And the lad o' my heart beside me.