Lenehan is one of several anglicized forms of two
Gaelic Irish surnames, Ó Leannacháin and Ó
Luingeachán, the former of Roscommon and the latter an area on
the Limerick and Tipperary border.
Ó Leannacháin of Roscommon appears
in early records, the most notable of whom was Maelciaran O'Lenechan
of Tuamna, in Boyle barony, a priest very highly praised in the
"Annals of Loch Ce" and by the Four Masters for his
numerous good qualities. He died in 1249. Also found in Sligo as
Lenaghan, in modern times they are represented by the political
dynasty of Lenihan of South Roscommon whose members have followed
careers in elected public office for several generations.
The Ó Luingeachán sept of Limerick
and Tipperary is nowadays the more numerous. Variously anglicized as
Lenehan, Lanahan, Linehan and so forth (sometimes with a misplaced
mac prefix), this family descends from a younger son of
the House of MacEniry (Lords of Connello) of Cappagh. They were
originally chiefs of a district forming the present barony of Upper
Third, in County Waterford, where, on the left bank of the river
Suir, and where the river receives the waters of the Clodagh, they
had a strong castle. They were dispossessed by the Purcells and the
De Grandisons, who expelled them from their patrimonial inheritance.
Afterwards they possessed Crota Cliach and Hy-Coonagh, a territory
partly in the barony of Owney and Arra, in Tipperary, and partly in
the barony of Coonagh, co. Limerick.