Ó Dalacháin
Ó DALACHÁIN—I—O Dallaghan, O Dolaghan, Dallaghan, Dolaghan, &c.; 'descendant of Dalachán' (diminutive of Dálach); the name of an ancient family in Tirconnell who were chiefs of Tuath Bladhach, now anglicised Doe, in the north of the barony of Kilmacrenan. In the 16th century, the name was found chiefly in the midlands, especially in Offaly, where the family was numerous and respectable. The castle of Liscloony, in the parish in Tisaran, the ruins of which are still to be seen, was built by Melaghlin O'Dalachain, in the year 1556. The anglicised forms of this surname cannot always be distinguished from those of Ó Dubhlacháin or Ó Duibhleacháin, which see.
Alphabetical Index to Irish Surnames