For those of you who have always wondered (!) the name CASSIDY means
"descendant of the curly-haired one." In Gaelic it is spelled Caiside. A man
with this name would use the O (with an accent over it) before Caiside, for
instance, Tomas O Caiside. In English, this is usually written O'Cassidy. But
unlike some other Gaelic names, most families have not retained the O.
Since the "s" sound in Gaelic is a soft "s", more like our
"sh," the
pronunciation of the name in Gaelic is closer to Cash-a-day. So, as our
ancestors, many of whom could not read or write, had their names written down
by non-Gaelic speakers, variations in spelling crept in. Hence we have
Cassidy, Cassady, Cassaday, Cassity, etc.
The name Cassidy is traced to County Fermanagh, and exists today most
frequently in the counties of Fermanagh, Monaghan, Cavan, and Donegal. The
Cassidys were traditionally physicians to the Maguires, the ruling Gaelic
family of Fermanagh, and to other northern chiefs. They also herenachs
(hereditary caretakers of church land) during the medieval period for the
parsih of Devinish. The family originally lived at Ballycassidy near
Enniskillen. Today it is the 5th most common native Gaelic name in Fermanagh.