M(a)cLaughlin /mɪˈklɒxlɪn/ is the most common Anglicized form of Mac Lochlainn, a masculine surname of Irish origin.
The original surname Mac/Nic Lochlainn was borne by a family of Cenél nEógain, a branch of the historic northern O'Neill dynasty, reputedly founded by Niall Noígíallach.
M(a)cLaughlin is sometimes used as a modern form of O'Melaghlin/Melaghlin, which is more commonly modernised McLoughlin, M'Loughlin, and O'Loughlin (among other spellings).
O'Melaghlin was a phonetic rendering into Anglo-Norman and Middle English of ó Mǽilsheáchlainn.
[3] M(a)cLaughlin and M(a)cLoughlin are rarely English forms of the surname ó/ní Lachtna, a phonetic corruption of the much more common Loughney or M(a)cLoughney.