In Irish surname books McCann is normally stated to be an anglicised form of the Gaelic surname Mac Canna which means 'son of Annadh.' Other forms in Gaelic are Mac Cana and Mac Anna. The McCanns were lords of Clann Breasail and originated on the south side of Loch Neagh in County Armagh. While this is certainly true for the majority of McCanns in Ireland and the Diaspora, DNA testing has revealed that McCann is some cases is the anglicised form of Mac Eáin. Mac Eáin is normally anglicised as McKean, McKane, etc., but occasionally as McCann.
The anglicising of Gaelic surnames was done very haphazardly and standard forms are rare. Fortunately DNA testing can often ascertain the correct original for of the McCann surname.
Not only is McCann sometimes a form of Mac Eáin, but the reverse is true also, in a few cases DNA testing revealed that McCane can also be a anglicised from of Mac Canna.