Translation according to P. W. Joyce:
Ballynalahagh in Cork and Limerick, and Ballynalahy in Galway ; Baile-na-lathaighe, the town of the slough or quagmire. For lathach, see vol. ii. p. 388 [reproduced below].
The Four Masters, when mentioning the place now called Bellaugh near Athlone, call it Lathach, which signifies mud, a slough, a puddle, a miry spot; and this word gives name to a good many places. It is seen in its simple form in Lahagh, east of Templemore in Tipperary, in Laghey near Dungannon in Tyrone, and in Laghy in Donegal; while we have Laghaghglass, green slough, in Galway. As a termination it usually takes some such form as lahy, as in Monalahy, north of Blarney in Cork, the moin or bog of the puddle; Gortnalahee in the same county, and Gortnalahagh near Castleconnell in Limerick, both signifying the field of the miry place. The diminutive, Laheen (little slough), is also the name of several places in Cavan, Donegal, and Leitrim.