The Clan/Sept History

The Irish name MacSheehy is derived from the Gaelic "Mac Sithigh," which is
probably derived from "sithigh," meaning "peace."

Spelling variations of this family name include: Sheehy, McSheehy, MacSheehy,
Sheehey, Sheehee, McSheehey, McSheehee, MacSheehey, MacSheehee, O'Sheehy and
many more.
First found in Limerick, where they have been seated from ancient times and it
is said that they arrived in Limerick about 1400, having come from the north
where they were a branch of the McDonnells of Antrim. The sept were
"gallowglasses," mercenary soldiers who fought for kings and chiefs. In Limerick
they served the Earl of Desmond and were seated near the town of Rathkeale.
Some of the first settlers of this family name or some of its variants were:
Edmund Sheehy, who arrived in Philadelphia in 1815; Cathn. Sheehy, who arrived
in Philadelphia in 1817; Edmond Sheehy, who arrived in Quebec in 1825; William
Sheehy, who was on record in Allegheny Coujty, PA in 1828.