McDaniel is a common surname across Ulster. It is almost always a anglicised form of the Gaelic surname of Mac Dónaill and can be either Irish or Scottish in origin. The root name is Dónall which means 'world mighty' and it is a very old and very common Gaelic personal name. Many of the McDaniel families participating in the Ulster Heritage DNA Project have matches to men surnamed McDonald, McDonnell, etc., showing how one Gaelic name will often have multiple anglicised forms.
Some of the McDonnell in Ulster additional will have matches to the historic Gaelic Clan, Clann Mhic Dhónaill, or Clan Donnell as they are often called in Ireland. They were a Gallóglaigh and Redshank clan found in great numbers in the Glens of Antrim, but also in other parts of Ulster. There is also native Irish McDaniels that descend from the Fermanagh clan Kelly. It is also good to keep in mind when doing family history that many McDaniels will not have any known clan connections and will be the descendants of a man named Dónaill whose sons took his name, a case of simply patronymics. McDaniel, McDonnell, and McDonald is one of the most numerous surnames across Ulster.