The personal name "Lochlan" or its variant in Irish, "Lachlan," forms the basis for the surname MacLochlainn (genitive form), meaning "son of Lochlan," commonly anglicised to MacLaughlin or MacLoughlin; or from "Mag," the variant form of "Mac," to MacGlaghlin, MacGloghlin, etc. In Scotland the name most often takes the form "Maclachlan," but is routinely anglicised to McLaughlin in other countries. Contrary to popular belief the form "Mac" was never limited to Scottish usage but was the original Irish form, abbreviated to "Mc" or "M'" by English scribes.

   The forms "McLaughlin" and "McLoughlin" are simply variants, based on the Irish variants of "Lochlan" and "Lachlan." The "au" form is today much more common, particularly in the north of Ireland, but the "ou" form may be found there as well. The "ou" form is more common in Connacht, Leinster, near Dublin and in the south of Ireland.

   The McLaughlins of Donegal based their surname on an ancestor named Lochlan, who lived about 1020 A.D. His grandson was Domnall MacLochlainn, the High King of Ireland, who died in 1121 A.D. This Domnall MacLochlainn is referred to in the "Annals of Ireland" as both "Domnall Ua Lochlan" and "Domnall Ua Neill," indicating he may have been the first of this line to assume the surname MacLochlainn. There is some supposition that Lochlan may have been the son of a Viking princess, although there is no support for this theory in the Annals of Ireland.

   Many interpretations have been advanced for the surname MacLochlainn, which is commonly said to have been of Norse origin, including "men of the fiord-land or lakes, strong at sea and sons of the sea." But these interpretations are based on the Irish root "Loch" meaning lough or lake and are clearly of Irish origin. In the ancient annals of Ireland, however, the homeland of the Norse invaders of the 9th and 10th centuries was invariably referred to by the annalists as "Lochlan," often found in the text as "Tir na Lochlannaigh" or the "land of the Norsemen."

   Norse scholars influenced by the work of Marstrander believe the name "Lochlan" was a corruption of the Norse "Rogaland," a region of Norway from which many of the first Norse invaders of the western isles emigrated. According to Marstrander, on an Irish tongue "Rogaland" would become Rochlann which would later become "Lochlann" under the influence of the second "L" and a folk-entymological association with Loch (Gaelic for lake). Irish experts (Woulfe and MacLysaght) indicate "Lochlan" was a Norse personal name, but there is no support for this thesis in traditional Norse genealogies and if the name did originate as a personal name amoung the Norse it did so in Ireland. Many have suggested that the name "Lochlan" therefor indicates intermarriage with the Norse and this may well have been the case, particularly in those families which were amoung the first to adopt the name.

Donnchadh O Corrain, Department of History, University College, Cork,  has written a long article on the derivation of the Norse place-name "Lochlan."  (THE VIKINGS IN SCOTLAND AND IRELAND IN THE NINTH CENTURY).  O Corrain believes that Lochlan originally referred to Viking Scotland, which included the Isle of Mann, and only later became the Irish word for Norway.

     Incidences of the MacLaughlin surname
     appearing throughout Ireland in 17th
     century documents.

1.   Co. Donegal   1659 Census

          Inishowen Barony

               McLaughlin   63
               McGlaghlin   76

           Barony of Boylagh and Bonagh

               McGlaghlin   14 

2.   Londonderry Co.

           Londonderry City and County

               McLaughlin   04

           Terkerin Barony

               McLaughlin   19

           Kenaght Barony

               McLaughlin   30

3.  Tyrone County     Hearth Money Rolls  1665

         Omagh Barony

            Longfield Parish

                 Philip McLaughlin of Sopgaly
                 Edmond     "            "

             Drumra Parish

                 Donold oge McLaughlin of Cullbuke

4.  Antrim County  1659 Census

         Baronys of Dunluce Carey and Kilconway

              McGloughlen   13

          State Papers  1663

              "The whole barony of Cary was by proviso set out    
           for the payment of part of the Marquis of Antrim's     
          debt, but was set out to .... "

                   List of names includes:  George McLaughlin

5.  Westmeath County   1659 Census

         Barony of Clonlonan

              McLaughlin   10

         Barony of Moygoishe

              Loughlin    07

6.  Kings County   1659 Census

         Barony of Garriecastle

              titulado:  Terence Melaghline, gent.
              townland:  Gallen

         Barony of Phillipstowne

              titulado:  Richard Loughlin, Esq.
              townland:  Clontrell

7.  Leitrim County   1659 Census

         Barony of Drumaheir and Rosclogeer

              McLoghlen   32

8.  Roscommon County   1659 Census

         Barony of Boyle

              McLaghlin   08

         Barony of Moycarnan

              MacLoughlin  05

         Barony of Ballentabber

              O'Melaghlin   11

              titulado:  Neile O'Melaghlin, gent.
              townland:  Cloonbellagh

9.  Sligo County   1659 Census

         Barony of Tyreragh

              McGillaghlen   03
              Loghlin        06

         Barony of Tyrerell

              McLoghln       15

         Barony of Culavin and Tiregh

              McGillaghlen   06
              Loghlin        06

10.  Wexford County   1659 Census

         Barony of Shelbyrne

              Loughnan       08

11.  Kilkenny County   1659 Census

         Barony of Gawran

              McLoghlin   11
              Loghman     06

12.  Limerick County   1659 Census

         Barony of Owny

              McLoghlen   05

         Persons transplanted in Ireland  
         O'Hart  "Landed Gentry"

             City and County of Limerick

                  McLoghlen, Faylen
                      "      Mary
                      "      Thomas
                  Loghlen, Catherine Ny
                     "     More Ny

13.  County Clare   1659 Census

          Barony of Burren

               McLoghlen   07
               O'Loghlen   06

               titulado:  Bryen O'Loghen, gent.
               townland:  Coskerine

          Barony of Tulla

               McLoghlen   12

          Barony of Bunratty

               Mcloghlin   10

14.  Tipperary County   1659 Census

          Barony of Clanwilliam

               McLoghlin   11

          Baronies of Eliogurty and Ikerim

               Loghlen and Meloghlen   10

          Barony of Iffay and Offay

               McLoghlen and Meloghlen   10

15.  Longford County   1659 Census

          Barony of Ardagh

               McLaughlin   15

16.  Louth County   1659 Census

          Barony of Atherdee

               McLoghlin   11

17.  Dublin County   1659 Census

          Barony of Balrothery

               Loghlin   09

           "An Inquiry into the ownership and tenancy
           of lands owned by the religious houses of
           the city of Dublin"
           "The Reformation in Dublin"  1536-1558

                 "Town of Mareton - two messuages, 40 ac.
                  arable, occupied by McLaghlyn and
                  McLaghlyn Oge, worth p.a., 40s."

     Special Report on Surnames in Ireland
     Matheson  1909
     Based on the birth indexes of 1890
     (five entries and upwards)

Surname   total births   By Province     Principle Counties

McLaughlin     391      Leinster  62   McLaughlin:  About 75% in
(var. McLoughlin)       Munster    7   Antrim, Donegal & L'Derry; 
                        Ulster   228   a few in Tyrone;  very few 
                        Connacht  94   very few elsewhere.
                                       McLoughlin:  Chiefly in    
                                       Dublin, and Connacht, but  
                                       found generally throughout 

O'Loughlin      40      Leinster  12   Principally found in Clare 
                        Munster   21   and Dublin.
                        Ulster     3
                        Connacht   4

Loughlin        57      Leinster  18   Loughlin:  Principally 
(var. Laughlin)         Munster    7   found in Leitrim, Dublin,  
                        Ulster    22   and Kilkenny. 
                        Connacht  10   Laughlin:  Principally     
                                       found in Tyrone & Antrim

Loughnane       13      Leinster   1
                        Munster    6
                        Ulster     0
                        Connacht   6

Loughman         9      Leinster   4
                        Munster    5
                        Ulster     0
                        Connacht   1

Loftus          34      Leinster   3   23 in Mayo
                        Munster    2
                        Ulster     0
                        Connacht  29

Lawton          10      Leinster   1   7 in Cork
                        Munster    7
                        Ulster     2
                        Connacht   0

     Principle Names (by Province and County)

                         Births in 1890


         Donegal:  Gallagher  196;  Doherty  160;  Boyle  102;    
                   O'Donnell  102;  McLaughlin  81;  Sweeney 50.

         L'Derry:  Doherty  80;  McLaughlin  68.

         Tyrone:   Quinn  40;  Mullan  39;  Kelly  38;
                   Donnelly  34;  Gallagher  34;  McKenna  33;    
                   Campbell  32;  Hughes  31;  Wilson  30;        
                   McLaughlin  29;  O'Neill  29.

         Fermanagh:  Maguire  44;  McManus  30;  Dolan  23;       
                     McGovern  23;  Johnston  22;  McHugh  20;    
                     Cassidy  17;  Wilson  15;  Thompson  14;     
                     Elliot  13;  Irvine  13;  McLoughlin  12.


         Leitrim:  Kelly  30;  Reynolds  30;  Flynn 20;
                   McLoughlin  20.

         Sligo:    Brennan  31;  McLoughlin 28.

     Surnames by Province

    Ulster          Connacht       Munster           Leinster

McLaughlin 228    McLoughlin 94   McLoughlin  7    McLoughlin 62
O'Loughlin   3    O'Loughlin  4   O'Loughlin 21    O'Loughlin 12
Loughlin    22    Loughlin   10   Loughlin    7    Loughlin   18
Lawton       2    Loughnane   6   Loughnane  13    Loughnane   1  
                  Loughman    1   Loughman    5    Loughman    9  
                  Loftus     29   Loftus      2    Loftus      3  
                                  Lawton      7    Lawton      1

Donegal           Leitrim         Clare            Kilkenny
Tyrone            Sligo           Cork             Dublin
Fermanagh         Mayo            Tipperary        Longford
L'Derry           Roscommon       Limerick         Louth
Antrim                                             Meath 
Down                                               Westmeath
Monaghan                                           King's Co.