Londonderry People & FamiliesSurnames of Magilligan ParishNew site which has some links for Co. Londonderry- see here for link to it as well as comments on problems viewing, etc.
www.rootschat.com/forum/index.php?topic=359576.msg2363343#msg2363343
The O'Cahan Princes of Ulster website contains a lot of information about the surnames on the following list The further back you go with your research the more you need to consider the spelling variations ... today you'll find that some families are reverting to the old spelling so some of the next generation of genealogists may have to start with the old spelling, then the present spelling and then the old spelling as they start researching their ancestors.
The Spelling Variations of O'Cahan ...
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.