It appears as though my independent Internets research was pretty spot on:
“The Lowry name and its numerous alternate spellings is likely more Scottish than Irish. If you search the online records of PRONI (the Public Records of Northern Ireland), you will see that the Lowry name is concentrated in County Down, particularly in the Kilmore, Killinchy and Killyleagh areas south of Belfast. If you look at a timeline, you will see few Lowry’s before 1650 which makes sense because the great Ulster Plantation experiment didn’t begin until the early 1600s when James I empowered two men named Montgomery and Hamilton to repopulate parts of Northern Ireland ravaged by war. County Down and County Antrim (directly north of Down) were to receive wave after wave of Lowland Scots who emigrated to Northern Ireland in search of a better life. Being Lowland, as opposed to Highland, they were almost uniformly Presbyterian and hardly Celtic. The Celtic people were largely Highland Scots as well as the Irish who populated the republic of Ireland, as well as Wales.
There is even some speculation that the Lowry name is French, being a corrupted version of Loire, the river valley in France where many French Protestants (Hugenotss) lived until moving elsewhere because of religious persecution…
As the name suggests, most of the emigrants from Northern Ireland to America were Scots who moved first to Northern Ireland. They are not Irish.”
A Lowland Lowrey 