Recorded in several known spellings including Killelay, Killeley, Killelea, and Kilalea, this is an Irish surname. It is almost certainly locational from the village of Killelagh in the county of Derry near the town of Maghera. This in itself is very unusual. Very few Irish surname are locational, almost all are patronymics, and often derived from nicknames for the earliest name holder or first chief of the clan or sept. Furthermore this surname does not appear to be listed amongst the surnames of Ireland, developed by the famous etymologist the late Edward MacLysaght. This is clearly an oversight, as there is little doubt as to its origin, it being well recorded in both surviving church registers for the counties of Roscommon and Galway, and in the Irish immigrants arrivals list for the port of New York, for the period of the infamous "Potato Famine" of 1846 - 1848. The first of these recordings is given as being that of Michael Lilleleagh, aged forty, a farm labourer, who left Ireland on the ship "Empire of Liverpool", on November 30th 1846. Later examples of recordings from church registers include Bridget Killelea who was christened at Ballinsloe, County Galway, on August 30th 1866, and Patrick Killelay who married Mary Burns at Aughrim, County Roscommon, on March 3rd 1867.