The Irish surname Connolly is an anglicization of the Gaelic names; Conghalie, a sept of Connacht, who were separated and dispersed as three distinct families based around the counties of Cork, Meath and Monahan. Where they were one of the "Four Tribes of Tara". In Monaghan, around 1591, Tirlogh O Connola is recorded as being Chief of his name. The OConghalaigh from conghal ( as fierce as a wolf) were based in Connacht, where the English version is now often spelled "Connelly". The name arose in West Cork as O Coingheallaigh, while Ulster Connollys derive from both the O Conghalaigh of Fermanagh, who gave their name to Derrygonnelly, Connollys Oakwood and the Monahan Connollys. The Monahans being the most predominant of the Connollys, recorded having 'Chiefs of the Name' up to the 17th century.
O'Conghalaigh"descendant of Conghalach"(the latter being a personal name meaning valorous) O'Conghalaigh, descendant of Conghallach' ( the latter a personal name meaning pledged). Septs of the name are associated with Connaught, Monaghan and Munster: that of Monaghan was in early times the most important being one of the Four Tribes of Tara. Once everyone was known by one name but this led to confusion and so an extra name was adopted.