My late Aunty Cath, the family historian, always told me that Corrigan, Kerrigan and Carrigan are a common derivation of CARRAIGIN, Irish for a"small rock".

In Irish the "gh" is pronounced more "k" so you would hear it pronounced as "carricken"

The prefix "O'" means "descendant of" and was commonly dropped to anglicise an irish name.

The Corrigan (O'Corrigan, Carrigan, Corocan, Courigan, Currigan) surname is of Irish origin. Corrigan means a "Spear" in Irish. It is believed to have originated from Coirdhecan in Eoghain. It is also believed to be connected to the Maguire clan. The Corrigan surname was common in the 17th century in County Fermanagh. Today it has spread across most of Ireland and to the United States and Canada.

The Irish sept Ó Corragáin, whose stronghold was in County Fermanagh, is the origin of the names Corrigan, Carrigan, Courigan, Corgan, and Currigan. Early records in the Annals of the Four Masters indicate the name was associated with clerics and abbots. It was well established during the Middle Ages, spreading south into the counties of Monaghan, Meath, Roscommon and Offaly. The village of Ballycorrigan near Nenagh in County Tipperary indicates the name also spread to that county.

Last name: Carrigan source...http://www.surnamedb.com/Surname/Carrigan 

Recorded in a wide variety of spellings including Carrigan, Courigan, Corrigan, Currigan and Carrocan, this is an Irish surname of great antiquity. Deriving from the Gaelic form of O' Corragain, the name like many Irish surnames is a form of descriptive nickname. It translates as "The descendant of the kin of Corra", the latter being an early pre 7th century baptismal name meaning "Spear". This was originally a name given to either a mighty soldier or hunter, both being equally popular in the ancient mythology of the country. It is said that the clan or sept, as it is usually known, belongs to the same grouping as the Maguires, both have lost the "O" prefix and both are mainly associated with Ulster, at least in origin, although widely scattered, the town of Ballycorrigan being situated in County Tipperary. Indeed these two "names" probably gave the English administration of Ireland more trouble than any other, which is strange as the original nameholders were reputed to be "men of the cloth". Sadly most early Irish records were destroyed in 1622 during the Irish Civil War, when the IRA in an act of typical mindless vandalism set fire to the Public Records office in Dublin. The early surviving recordings include such eminent persons as Sir Dominic Corrigan MD, (1802 - 1880), an eminent physician in Dublin, and the Rev. Michael Corrigan (1839 - 1902) Archbishop of New York. The first known recording is beliebved to be that of Gillan O' Corragain, the abbot of Willin, county Fermanagh, in 1534.

Carrigan can also be a Townland, parish (RC or Church of Ireland), an actual town or simply a common name for a rocky place. This led me on some wild goose chases during my research. There are more than one Carrigan, Ballycastle, and many other place names....so dont rely soley on digital maps.
Read more: http://www.surnamedb.com/Surname/Carrigan#ixzz4UU3p6mHz

CARRAIG , or "big rock" as in Carrick-a-Rede, the well known rope bridge out to a big rock near Ballintoy in the north of Ireland and the name of a local hotel that was run by Patrick and Sarah Jane and their 10 children, the original O'Carrigans between 1908 and 1927**

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pictures above and below...Carrigans is a small town west of Derry in the north of Ireland....I added the O' in the picture above.

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