Recorded in many spellings forms including McGillooly, Gilhoolie, Gilhooley, Gilhooly, Gilhouley, Gilluley, and in some parts of the country Gilhool, this is a famous Irish surname. It originates from the pre 10th century Gaelic surname 'Mac giolla Ghuala', which translates literally as 'The son of the follower of the Shoulder'. The sept are a branch of the Clan O'Mulvey, and this may account for the unusual meaning. The majority of Irish Gaelic surnames were originaly nicknames for the first chief of the family. These nicknames were very varied, many were clearly abstract, but others, like English nicknames, were probably more physical, referring to some particular appearance of this man. In this case we incline to the abstract, and a possible reference to the loss by the O'Mulveys of one of their strong points, and in a transferred sense, a 'shoulder' on which they may have relied for support. However it has to be said that with all medieval nicknames from anywhere, a large measure of conjecture has to be applied, and almost nothing is proven for certain. What is also interesting and may have a bearing on the meaning is that the sept were famous for the number of priests that they have provided to the Roman Catholic Church. These are known to have commenced as early as 1461 down to the 20th century. Examples include: Teig M'Gilhooly who was the priest of Kitoghert, in County Leitrim, whilst two centuries later in 1657, another Teag MacGillooly was recorded at Granard, County Longford. The sept did not escape the worst of the infamous Potato Famine of 1846-1848, many members leaving the country at this time. Amongst the first of these refugees were James and Jane Gilhooley, who sailed for New York on the ship 'Emanuel of Liverpool' on April 3rd 1846.