There is an 1872 Court Order concerning the Parcel of Land on the West Side of Charles-street South, Sandy Row, Belfast, Ireland, which records that at house number 101 John McIlhaggart was a tenant paying an annual rent of £7.3.0. He was a "weekly tenant, tenancy determinable on Monday in any week". This day was legally known as a Gale Day. There is a marginal note that byways and light are preserved and that the landlord pays all the taxes of the tenants.
I think this could be the John or Jonathan McIlhagga who two years previously had married Margaret Douglas. By 1972 they had had their first two children, daughters Hannah and Jane. These were the first two of eight children. There is no other note of this address that I know of, relating to that time.