O'Laithbheartaigh

"An old Gaelic name"

The origins of this  name are listed in Robert Bell's "Book of Ulster Surnames". There are six Celtic nations - Breton, Cornwall, Ireland, Isle of Man, Scotland, and Wales. There are two languages used by the Celts - Gaelic used by the Irish, Manx and Scots and Brythonic used by the other three nations. There were large language settlements of Laffertys in counties Antrim, Donegal, and Tyrone and smaller settlements in counties Armagh, Down and Londonderry (or Doire in the days pre 1600, when there may have been a larger settlement of Laffertys there). The settlements in counties Antrim and Donegal indicate that many Laffertys came from Scotland (the shortest sea crossing between Antrim and Scotland is about 12 miles). This however is speculation since Lafferty is predominantly an Irish Surname.

Surname Dictionary/Sloinnte na h-eireann

Lafferty - fairly numerous: Galway-Mayo, Ulster etc. an aspirated form of Flaherty, q.v. the family were important in Tyrone and Donegal in the 16th century.

Laverty - numerous: Ulster generally. Louth, Galway etc. Sept of Donegal and Tyrone. Cognate with O'Flaherty but a distinct Ulster grouping.

Lafferty/Laverty

Lafferty is an exclusively Ulster name and in 1900 was found only in the countries of Donegal, Derry, and Tyrone in Ireland. It stems mainly from O'Lafferty or O'Laverty. Both names derive from the Gaelic for "bright ruler" and are Ulster forms of the Connacht name O'Flaverty or O'Flaherty. The 'F' in Ulster was often aspirated or silent, thus O'Flynn becomes O'Lynn.

Lafferty:
This name is common in Donegal, Tyronre and Derry and extends from the gaelic name, "O'Laithbheartaigh"The Lafferty's were descendants from the Lord of Aileach, famous for the great stone fortress, the Granian of Aileach. The first to bear the name was Murchadh Ua Flaithbheartaigh of the Eagle Knee, King of Tyrone, who died in 972. In the 13th. Century there were many Lafferty's living in the Finn Valley and also in the Lagan. However, they were driven from their rich lands by the O'Neill's and settled at Ardstraw, Co. Tyrone. There is a townland near there called Lislafferty.