MOB,
You asked if the first name Ismay was common anywhere. The short answer is no. In the 1901 Irish census there were just 16 (out of a population of 4.4 million.). You can see where they lived using this website (just enter the forename only). None in Carlow.
https://www.census.nationalarchives.ie/search/
As a surname, Ismay is known in Ireland (a bit) because of the Titanic. Joseph Bruce Ismay was an Englishman who was Chairman of the White Star Line (owners of the Titanic) and on board when it sank in 1912. In spite of the general rules about “women and children first” getting in the lifeboats, Ismay managed to get a place in one and survived. However his personal reputation was shattered for ever for deserting the ship, when the Captain went down with his ship.
There was an Ismay Bruce in Ireland in the 1901 Irish census (with her daughter Ismay). There is perhaps some connection with Joseph Bruce Ismay.
https://www.census.nationalarchives.ie/pages/1901/Kilkenny/Castlecomer/Moyhora/1459591/