Bondgirl,
w.r.t. "Killarlah":
The OSNI map for Strangford Lough (Sheet 21) shows an antiquity called "Killaresy Church".
It lies on the A22 road almost midway between Killinchy and Killyleagh.
[Just N of "Toy & Kirkland", with "Ballymacromwell Lough" nearby.]
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Some other possibilities for Ireland are:
Killala (Co. Mayo)
Killalan (Co. Galway)
Killarga (Co. Leitrim)
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You may wish to consider a "Land of Oz" connection.
There is a place named Killara near Melbourne, Victoria.
[Also a Killinchy.]
That SW corner of the continent had "gold fever" in the mid 19thC, with many folks from Britain and Ireland rushing out to make their fortune.
[Your folks may have "come over" in order to catch one of the larger emigrant ships.]
Most returned disillusioned & broke within 10 years.
Another Killara lies near Casterton, near Coleraine, in the Grampian Highlands. Yet another is a posh suburb of Sydney.
A Killara B&B is 10Km from the town of "Port Fairy", which called itself Belfast for a while during the 19thC.
[The name is Aboriginal, meaning "permanent settlement".]
Many LDS records do not obviously distinguish in which continent a mentioned town is extant.
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Great "Giraffe GIF" that - my nieces loved it!
All the best.
Martini time!
Agent J