Slattery, ó Slararra A Gaelic surname derived from Slatra meaning ‘bold, strong’. A sept of the Dál gCais formerly seated at Ballyslattery (also called Newgrove) in the Barony of Tulla Upper in Clare, who later dispersed throughout Munster. In 1890 Slattery was principally found in Tipperary, Kerry, Cork, Clare and Limerick, and the estimated number of bearers was 3,090. In the United States Slattery is the 4,410th most numerous surname with an estimated 8,250 bearers.