The origins of the surname O'Cathain is derives from Cathasach, a grandson of Drugan when the surname makes its first appearance in the annuals;
"Raghnall mac Iomhair I Cathain tigherna na Craoibhe, Ciannachta Fear Li"
meets his end from violence. It took over 300 years for that powerful stock to emerge from the congeries of families that constitute Clan Connor. Like Kane, Keane is an anglicisation of O'Cathain, from a diminutive of cath, meaning "battle".
O'Kane is the anglicised form of O'Cahan and is variously rendered as Kane, Keane, Kayne, Keaney, O'Keeny, Keyne, Cahan, O'Cain, Cain and Keny. In addition, it embraces McAvinney, McEvinney and McQueen. Another large sub-sept of O'Cahan is McCloskey (McCluskey, Cluskey and McLuskey), a numerous north Derry name. McCloskey derives from Bloscaidh O'Cathain (Bloskey O'Kane), who, in 1196, slew Murtagh O'Loughlin, heir to the Irish throne. Other Variant Spellings ; Cahan, Cain, Cane, Gahan, Kain, Kaine, Kane, Kean, McAvinney, McCain, McCloskey, McEvinney, McKain, McKane, McKean, MucKian, O'Cahan, O'Caughan, O'Kane.
In the parish of Killelagh, Kane appears in the name of the townland which may point to the original settlcment of the O'Cahans, or Kanes, Tirkane (the country of Kane), and Half Gayne (the stone house of Kane).