Milligan, Milliken
Milligan, Milliken—These two names are of the "O" septs in Galloway; in Gaelic O'Maolagain. The name is common in Dumfries County and in North-East Ulster.
Alphabetical Index of Anglicised Surnames in Ireland
See also Woulfe’s Irish Names and Surnames
… and O'Hart's Irish Pedigrees