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 and Mc together example has been taken as representative of a possible paradigm. A book on filing rules from 1918 gives an example showing Mc and M' treated as abbreviations, i.e. for Mac, and ordered as if in the expanded version; and a similar book from 1922 makes the rule one of a number that apply also to St. (Saint) and Mrs. (Mistress). A 1938 book that is a comparative study of cataloguing in various British libraries regarded Mac + Mc + M' sorting as an example of achieved "standardisation" in alphabetisation. It gave further examples where, it argued, such standardisation would be