The Casserly Family

The Casserly surname derives from the Gaelic Mac Casarlaigh — son of Casarlach — and belongs to County Roscommon in Connacht. The personal name from which the surname descends is relatively unusual in the Gaelic naming tradition, and the sept was never among the great powers of Connacht; they were instead one of the many families of middling standing who provided the social fabric of Gaelic territorial life.

The O'Conor dynasty — the greatest ruling family of Connacht and the last High Kings of Ireland — provided the political framework within which families like the Casserlys operated. Roscommon was the heartland of O'Conor power, and the town of Roscommon with its castle was a major royal centre. The Casserly sept held local positions within this framework: farmers, local chieftains, and occasionally clerical or bardic roles.

The Anglo-Norman incursion into Connacht in the 13th century brought the De Burgh (Burke) family as the dominant power, but the Gaelic families of Roscommon maintained considerable continuity underneath Norman lordship. The Casserlys, not being major landowners, had less to lose and survived the Norman period with their community identity largely intact.

The 17th century brought more severe disruption. The Cromwellian settlement classified Connacht as the destination for dispossessed Catholic Irish from across Ireland, and while this brought newcomers into the province, it also placed the existing Connacht families under enormous pressure. The Casserly families of Roscommon faced the same pressures of rack-renting and religious discrimination that defined Irish Catholic life under the Penal Laws.

Famine emigration from Roscommon in the 1840s and 1850s dispersed Casserly families to the United States, principally to New York and the New England states. The surname remains most common in Roscommon and east Mayo today.