It was introduced by Ella Logan in the original Broadway production of Finian's Rainbow.
There is no actual Glocca Morra in Ireland (though there is a Glockamara). In a television interview late in his life, Harburg revealed that the name "Glocca Morra" was made up by composer Lane, who had devised a dummy lyric beginning with the line, "There's a glen in Glocca Morra". Harburg liked the name but insisted on changing the line to, "How are things in Glocca Morra?", as this is more personal and immediately evocative of nostalgia and homesickness. However, James Stephens' work, The Crock of Gold (first published in 1912) refers to "the leprechauns of Gort na Gloca Mora" ("the field of the big rock" in Gaelic), and there would appear to be little doubt that this formed the basis for the place-name of the song's title.
I hear a bird, Londonderry bird, It well may be he's bringing me a cheering word. I hear a breeze, a River Shanon breeze, It well may be it's followed me across the seas. Then tell me please:
How are things in Glocca Morra? Is that little brook still leaping there? Does it still run down to Donny cove? Through Killybegs, Kilkerry and Kildare?
How are things in Glocca Mora? Is that willow tree still weeping there? Does that lassie with the twinklin' eye Come smilin' by and does she walk away, Sad and dreamy there not to see me there?
So I ask each weepin' willow and each brook along the way, And each lass that comes a-sighin' Tooralay How are things in Glocca Morra This fine day?