a historical county of W Northern Ireland, occupying almost a quarter of the total area of Northern Ireland; in 1973 its administrative functions were devolved to several district councils
Ir. county, from Ir. Tir Eoghain "Eoghan's Land," from Eoghan "Owen," ancestor of the O'Neills, who owned land here. Tir also forms the final syllable in Leinster, Munster, Ulster.