Likewise there are just two occasions when the variant McIllhagga has been used. The first is on a New York Passenger Arrival List (Ellis Island), 1892-1924. Catherine departed from Liverpool on the ship Saint Louis, arriving in New York on 9th September 1916, when she was 30 years old. Her 'ethnicity' is given as Gt. Britain, Scotch. She was single, and would have been born in 1886. In my indexes there are two people this could be. One was Catherine McIltaggart, daughter of Richard McIltaggart and Mary McArevey on 14th November 1886. The other was Catherine McCulloch McIlhagga, born 17th May 1886 to James McIlhagga and Johanna McCulloch. We know that she remained single and ended up in Hillsborough, Florida, where she died aged 59. We can be sure that this was one and the same as Catherine McIllhagga who was on the ship to Saint Louis. The second McIllhagga documentation is the birth record of Robert in Dublin South, in the October to December Quarter 1941. Oddly a mother's maiden name is given, Robinson, but not a father's name. His mother was in fact Madeline Robinson and his father Richard McIlhagga, a Race Horse Trainer and Owner. So we see that both occurrences of McIllhagga were misreadings of McIlhagga.
It is obviously so easy to mishear a final vowel at the end of a four syllable name like McIlhagga, so that it becomes McIlhagge; or indeed it is equally easy to mispronounce the 'a' to sound like an 'e'. We have three examples of the variant McIlhagge, two of which to my knowledge should certainly be McIlhagga. They both come from the late 19th Century. The first is the birth record of Hannah McCarrol Linton on 14th July 1879, in Ballymena, County Antrim. Her father was Robert Linton and her mother's name is recorded as Anne McIlhagge in the Ireland Births and Baptisms, 1620-1881. From other records, I think that 'Anne' should have been spelled without an 'e' and her surname should certainly have been McIlhagga. She was a daughter of William McIlhagga and Agnes McCosh. Hannah was the youngest of eight children who eventually in 1904 married Robert Fersugon. Our second example is of a fairly close relative, Agnes who at the age of 21, on 26th June 1898, married William Graham in Kirkdale, Lancashire, England. She was a daughter of Crawford, a son of William and Agnes above. In the England Marriages, 1538-1973 the surname of both father and daughter is spelled McIlhagge, but again it should have been McIlhagga. Finally, there is another English marriage which I confess I cannot yet put into a family tree. It is the marriage on 23rd April 1889 in Fleetwood, Lancashire of Jane McIlhagge to George Taylor Birkett. Jane's father was Henry who I know was originally from Donegore, a townland near the town of Antrim, and who was married to Agnes Stevenson. I know that a McIlhagga family did move from Ireland to the north-west of England, and Jane may have been part of it, so I suspect this is a third case of 'McIlhagge should be McIlhagga'.