Corcoran is an Irish surname of which the original Gaelic version being Ó Corcráin meaning "descendant of Corcrán". The name itself is derived from corcair meaning "purple".
The name Corcoran is an anglicisation of the names of two Gaelic clans. The first was the Ó Corcráin in Ulster. The second was the MacCorcráin clan from Leinster, which was a sept of Ó Corcráin. Related variations of the name Corcoran historically include MacCorcoran, O'Corcoran, and Corcorran. The Corcorans were predominantly from Fermanagh and included a number of figures of historical importance such as the Bishop of Clogher in 1370 and Edmund O'Corcoran, "the hero of Limerick" (from the siege of 1691).
Many Corcorans become members of the clergy between the tenth and fifteenth centuries, they became based around the vicinity of Lough Erne, County Fermanagh in Ulster. One member of the family, John Corcoran was appointed Bishop of Clogher in 1373.
The O'Corcrain territory was invaded by the Normans in 1170 AD.
During the Plantation of Ulster and the Cromwellian conquest of Ireland in 1649 AD, the Corcorans were scattered. Many settled on lands in Connaught, Munster and Leinster. Principally Offaly, Tipperary and Galway where the MacCorcorans had settled previously.