[...Kerrigan, ó Ciaragáin A Gaelic surname meaning descendant of Ciaragán (diminutive of ciar meaning ‘black’). A sept of the Ui Fiachrach, formerly seated at Baile Ui Chiaragain (Ballykerrigan) in the parish of Balla in Mayo. In north Galway it is often translated as Comber and Comer, from its supposed connection with cíor meaning a ‘comb’. In 1890 the surname was principally found in Mayo and Donegal, and the estimated number of bearers was 1,840. In the United States it is the 6,433rd most numerous surname with an estimated 5,500 bearers....]
the above text is taken from the following website:http://freepages.genealogy.rootsweb.com/~irishancestors/Surnames/Surnames%20in%20Ireland/KerriganLewis/Kerrigan.html
Caragan is a surname and a variant of Kerrigan. I don't know if Caragan is used as a firstname too, but it is quite common with Irish surnames that they are used as firstnames too, e.g. Gallagher
. That is because those surnames are often patronyms meaning 'son of...', and thus used to be firstname in ancient history.