Irish name#Surnames and prefixes

{{See also|Epithet}}

A first name may be modified by an adjective to distinguish its bearer from other people with the same name. {{lang|ga|Mór}} ("big") and {{lang|ga|Óg}} ("young") are used to distinguish parent and child, like "senior" and "junior" are used in English, but are placed between the given name and the surname, e.g. {{lang|ga|Seán Óg Ó Súilleabháin}} corresponds to "John O'Sullivan Jr." (anglicised surnames often omit {{vr|O'}}, leaving no trace of original {{lang|ga|Ó}}).

The word {{lang|ga|Beag}} ("little") can be used in place of {{lang|ga|Óg}}. This does not necessarily indicate that the younger person is smaller in stature, merely younger than their parent or in some cases to imply a baby was small, possibly premature, at birth.

Adjectives denoting hair colour may also be used, especially informally, e.g. {{lang|ga|Pádraig Rua}} ("red-haired Patrick"), {{lang|ga|Máire Bhán}} ("fair-haired Mary").

Colloquially in {{lang|ga|Gaeltachtaí}} (Irish-speaking areas) and some other areas it remains customary to use a name formed by the first name (or nickname), followed by the father and the paternal grandfather's name, both in the genitive case, e.g. {{lang|ga|Seán Ó Cathasaigh}} (Seán O'Casey), son of {{lang|ga|Pól}}, son of {{lang|ga|Séamus}}, would be known to his neighbours as {{lang|ga|Seán Phóil Shéamuis}}. Occasionally, if the mother or grandmother was a well-known person locally, her name may be used instead. If the mother's name is used, then the maternal grandfather or grandmother may follow it, e.g. {{lang|ga|Máire Sally Eoghain}}.

This system can be particularly useful for distinguishing people who live in the same area and who share a common surname but are not closely related, e.g. two people named John McEldowney might be known as "John Patsy Dan" and "John Mary Philip" respectively. Even the Irish forms sometimes survive in parts of the Sperrins, so that among the principal families of Glenullin some branches are known by father/grandfather forms such as {{lang|ga|Pháidí Shéamais}} or {{lang|ga|Bhrian Dhónaill}}.

A man's surname is generally formed by {{lang|ga|Ó}} ("descendant"; historically {{lang|ga|Ua}}) or {{lang|ga|Mac}} ("son") followed by a name or definite noun (often a profession) in the genitive case, e.g. {{lang|ga|Ó Dónaill}} (literally "descendant of Dónall") and {{lang|ga|Mac Siúrtáin}} (literally "son of Jordan"). When {{lang|ga|Ó}} is followed by a vowel, a (lowercase) {{vr|h}} is attached to the vowel, e.g. {{lang|ga|Ó hUiginn}} (O'Higgins) or {{lang|ga|Ó hAodha}} (Hughes).

A woman's surname replaces {{lang|ga|Ó}} with {{lang|ga|Ní}} (reduction of {{lang|ga|Iníon Uí}} "descendant's daughter") and {{lang|ga|Mac}} with {{lang|ga|Nic}} (reduction of {{lang|ga|Iníon Mhic}} "son's daughter"). In both cases the following name undergoes lenition, except for when {{lang|ga|Nic}} is followed by {{vr|c}} or {{vr|g}}. Thus the daughter of {{lang|ga|Seán Ó Dónaill}} has the surname {{lang|ga|Ní Dhónaill}} and the daughter of a {{lang|ga|Pól Mac Siúrtáin}} has the surname {{lang|ga|Nic Shiúrtáin}}. In Ulster it is common for a woman who adopts her husband name to just use {{lang|ga|Ní}} or {{lang|ga|Nic}} rather than the forms seen below.

If a woman marries a man, she may choose to take his surname. In this case, {{lang|ga|Ó}} is replaced by {{lang|ga|Bean Uí}} ("descendant's wife") and {{lang|ga|Mac}} by {{lang|ga|Bean Mhic}} ("son's wife"). In both cases {{lang|ga|Bean}} may be omitted, which results in {{lang|ga|Uí}} or {{lang|ga|Mhic}}. In both cases the following name undergoes lenition, except for when {{lang|ga|Mhic}} is followed by {{vr|c}} or {{vr|g}}. Thus a woman marrying {{lang|ga|Seán Ó Dónaill}} may choose to adopt {{lang|ga|Bean Uí Dhónaill}} or {{lang|ga|Uí Dhónaill}} as her surname and a woman marrying {{lang|ga|Pól Mac Siúrtáin}} may choose to adopt {{lang|ga|Bean Mhic Siúrtáin}} or {{lang|ga|Mhic Siúrtáin}} as her surname.

{{lang|ga|Mag}}, {{lang|ga|Nig}}, and {{lang|ga|Mhig}} are sometimes used instead of {{lang|ga|Mac}}, {{lang|ga|Nic}}, and {{lang|ga|Mhic}} before a vowel or {{vr|fh}} (which is silent) followed by a vowel.

Norman surnames formed by {{lang|ga|de}} (always lowercase; "of") followed by a name, e.g. {{lang|ga|de Búrca}} (Burke), {{lang|ga|de Paor}} (Power), or {{lang|ga|de hÍde}} (Hide, Hyde).

Some names consist of {{lang|ga|Mac Giolla}} ("servant's son") or {{lang|ga|Ó Maoil}} ("follower's descendent") followed by a name in the genitive case, e.g. {{lang|ga|Mac Giolla Phádraig}}, {{lang|ga|Ó Maoil Eoin}}.

Many Irish people use English (or anglicised) forms of their names in English-language contexts and Irish forms in Irish-language contexts. The Irish names of some people more famous under their English names include:

Other people are generally better known by their Irish name than by their English name, including the following:

{{unreferenced section|date=May 2010}}

• List of Irish-language given names
• Celtic onomastics
• Place names in Ireland
• Scottish Gaelic name
• Welsh surnames

{{reflist}}

• [http://braesicke.de/ainm.htm Names - Nualeargas]
• [http://www.libraryireland.com/Names.php Irish Names] at LibraryIreland.com
• [http://www.irishtimes.com/ancestor/magazine/surname The Origins of Irish Surnames] at IrishTimes.com ([https://web.archive.org/web/20160314005311/https://www.irishtimes.com/ancestor/magazine/surname/ Archive])
• [http://www.dubliner.com/ireland/irish-family-names Find Irish Family Names] at Dubliner.com
• [http://medievalscotland.org/kmo/Woulfe/index.shtml 16th & 17th Century Anglicized Irish Surnames from Woulfe] by MedievalScotland.org

{{Gaelic names}}

{{Names in world cultures}}

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{{Irish linguistics}}

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