Ó Casáin
Ó CASÁIN—I—O Cossane, O Kessan, O Kissane, Cussane, Kissane, (Cashman, Patterson); 'descendant of Casán' (diminutive of cas, bent, curly, &c.); the name of a Galway family, formerly seated in Ui Maine, Co. Galway; still represented in that county, but pronounced Ó Cosáin, and anglicised Cussane and Patterson. It is also a not uncommon surname in Kerry and Cork, where it is corrupted to Ó Ciosáin, and anglicised Kissane in the former county, and, very corruptly, Cashman in the latter.
Alphabetical Index to Irish Surnames