Patronymic was used by illegitimate royal children who were acknowledged as such by their fathers. The use of "Mac" in some form was prevalent in Scottish Gaelic, Irish and Manx, in all of which it denotes "son". "Mc" is also a frequent anglicisation in both Scotland and Ireland. In Ireland, the forms "Mag" and "M'" are encountered. The prefix "Mac" is used to form a patronym, such as "Mac Coinnich" – or the anglicized 'Mackenzie' – son of Coinneach/Kenneth. The female equivalent of "Mac" is "Nic", condensed from "nighean mhic" (in Scottish Gaelic) or "iníon mhic" (in Irish), both meaning daughter.
Mac Aodhagáin Flann Mac Aodhagáin up to the year 1643. The surname has been Anglicised in a variety of ways, including as Mac Egan, Egan, Eagan, Keegan, or Keigan, McKiegan, and McKagan. Muirchertach Mac Aodhagáin Muirchertach Mac Aodhagáin Muirchertach Mac Aodhagáin Muirchertach Mac Aodhagáin Muirchertach Mac Aodhagáin Muirchertach Mac Aodhagáin Muirchertach Mac Aodhagáin Mac Aodhagáin Mac Aodhagáin (English: Egan or Keegan), is an Irish Gaelic clan of Brehons who were hereditary lawyers - firstly to the Ó Conchobhair Kings of Connacht, and later to the Burkes of Clanricarde. The earliest surviving Irish law manuscript, "In Senchas Már", was written prior to 1350