Categories of surnames found in Ireland: 
Gaelic Irish surnames, born by the aboriginal population from the time when surnames were adopted (900 to 1100)
Viking or Ostman surnames, from Scandinavia or Scotland, same time range
Anglo-Norman surnames, mostly English, Welsh, Scottish, Norman, 1170 to 1300
British surnames, mostly from England and Scotland, planted in various parts of Ireland 1540 to 1700
Modern introductions, 1980s onwards
Why is surname research relevant to genealogy?
Theoretically one’s surname preserves the name of a direct male ancestor who may have lived up to 1,200 years ago
Why theoretically?
Non marital event as uncovered through y-chromosome dna studies: result, illegitimate surname, not the ancestral surname
Theory is that in the Irish medieval clan society, servants and followers took on the name of the overlord and thus lost their own surnames
Yet the bulk of y-dna studies do confirm one or two main groups per single surname: conclusion, the majority of people do bear the correct ancestral surname
Therefore one’s surname is a valuable heirloom. When genealogy is complete, and inevitably fails due to absence of records, only two methods of continuing the family tree remain, surname research and y-dna research
There are five types of Irish surname
Descriptive: describing the physical characteristics of the ancestor: Short
Occupational: based on the occupation of the ancestor when the name was adopted: Fuller
Cognomenic: based on a nickname given to the ancestor: Dullard (= idiot)
Toponymical: based on the place the ancestor came from: Landers (of London)
Ancestral: based on the forename of the ancestor: MacMahon
Descriptive:
White, Russell (red haired), Brown, Black, Hoare (white haired), Grace (‘fat’), Short, all Anglo-Norman or later British origin
Occupational:
Fletcher, Webb, Carpenter, Smith, Fuller, Baker, Archer, Brewer, Marshall
Cognomenic:
Savage (‘woodsman’, rustic, culchie), Dollard (‘fool’), Busher (‘butcher’), Cott\Codd (‘scrotum’), Purcell (‘piglet’), Lawless, Magner, Bowler\Fowler (‘bird hunter’). All Anglo-Norman or later British
Toponymical:
Cogan, Roche, Barry, Kennefick, Prendergast, Nagle, Stackpool, Condon (all places in south Wales)
Hodnett, Kent, Stanton, Bermingham, Burke (places in England)
Tobin, de Courcy, Nugent, Devereaux, Prendeville, Power (places in France)
All the above are Anglo-Norman or British. In the same category are some Irish surnames, i.e. Mead, Galway, Ardagh
Some names denote nationality:
Walsh, English, Lombard (Italian), Fleming (from Flanders), French, Brett (Breton), Ireland, Scott
Ancestral:
Associated with both Irish Gaelic and Anglo-Norman surnames. Aylward, Nicholson, Anderson, Henderson, Richardson, Rogers, FitzGerald, FitzGibbon. These are non native Irish examples. Almost all Irish surnames are ancestral
Anglo-Norman surnames arrive in Ireland in the period 1170-1300, British surnames in the period 1550 onwards. Viking surnames are earlier still but there are very few.
Gaelic Irish surnames
- These are of ancestral type
- Two main categories, O and Mac
- Ua = grandson of
- Mac = son of
- “By Mac and O you’ll always know true Irishmen they say
But if they lack both O and Mac, no Irishmen are they”
- The Irish were probably the first to use surnames, introduced between 900 to 1100 AD
- Ua is the earlier fashion. By the late 1000s the style ‘mac meic’, son of the son of, comes in as an alternative to Ua. After 50 years or so this changes to simple ‘mac’ (Mac Meic Carthaig becomes MacCarthaig or McCarthy)
In Ireland it is almost always the name of direct paternal ancestors or papponymics which is used to form the surname: these are patrilineal surnames from the father. In some societies descent was matrilineal, through the mother.
For example, the Picts in Scotland, the Tuareg in the Sahara
How were such names chosen?
- Some were used to commemorate an important ancestor, examples Brian Boru 1014, Ceallacháin of Cashel 956, Ruarc 898 (O’Rourke), Niall Glúndúb 919 (O’Neill), Fáelán 966 (Phelan), Dondubán 980 (O’Donovan), Cartach 1045 McCarthy) (Mathgaman 1129 McMahon).
- Some surnames were probably adopted casually, due to fashion. Often the name occurs in the pedigrees but is otherwise anonymous, frequently with famous ancestors and descendants (Cáem O’Keeffe), Cellach (O’Kelly), Flaitbertach, O’Flaherty) Súildubán (O’Sullivan, real name Echach, a nickname meaning ‘hawk eye’), Cruadláech (O’Crowley, real name is Diarmait, nickname is ‘warrior’), Mathgaman, McMahon)
Remember that many surnames represent unrelated families. O’Connor, 7 septs, O’Murphy, at least 4 septs. O’Flanagan, 6 septs. When performing research bear this in mind
Walsh: many different and unrelated families occur, a generic term for the hundreds of Welshmen who settled in various parts of Ireland with the Normans
Why are some surnames more common than others?
- The principle of ramification by powerful lineages
- Lesser septs acquiring hereditary ‘service’ roles with the great lineages
- Powerful medieval chieftains have several wives in succession, usually young, divorce is normal (for women as well), may have several mistresses as well (concubines), and probably impregnate some servants also
- Then we have the custom of the ‘naming’ of children (born of casual relationships and afterwards affiliated by the sworn declaration of their mothers, usually when near death)
- Illegitimacy is unknown under the Irish Brehon Laws, all sons have an equal claim to succeed the father as chief
- This results in chieftains having many sons, ‘portions’ for which have to be found for each. Hence pressure for the ‘clan’ to expand and acquire territory from neighbouring clans or from unrelated clans who hold territory within the lordship of the powerful lineage
Example 1: Richard Burke, earl of Clanrickard, who died in 1582, had six wives
Example 2: Conn Bacach O’Neill, earl of Tyrone, who died in 1558, admitted to siring over two dozen sons by various women
- One was Mathew Kelly, the blacksmiths son from Dundalk. His mother had ‘named’ him as a son of O’Neill whom she claimed to have had a relationship with
- ‘Naming’ was a common practice where women on their death bed ‘name’ a son to a different father than had been thought. The great lords rarely refused such sons, who under Brehon Law had as much right to succeed as all the others
- Mathew, renamed Fear Dorcha, won the contest to succeed his father. Mathew was the father to Hugh O’Neill, the great Earl of Tyrone
- All of this does not do much for the accuracy of the O’Neill dna lines
Examples of septs in service roles with greater lords:
O’Ahearne, originated in Co. Clare. An early connection with the FitzGeralds of Desmond in east Clare. Later, when the FitzGeralds expand into east Cork in the 1400s the Ahearns become plentyful there as tenants, stewards and yeomen to the Geraldines. Today most Ahearns are found in east Cork