| Surname | Individuals |
|---|---|
|
O'Brian
|
1 |
|
O'Brien
|
26 |
|
O'Connell
|
2 |
|
O'Donnell
|
1 |
|
O'Donoghue
|
1 |
|
O'Grady
|
2 |
|
O'Keefe
|
5 |
|
O'Leary
|
1 |
|
O'Malley
|
1 |
|
O'Neil
|
1 |
|
O'Neill
|
15 |
|
O'Reiley
|
1 |
|
O'Rourke
|
1 |
|
O'Shea
|
1 |
|
O'Toole
|
1 |
|
Oades
|
1 |
|
Oakley
|
7 |
|
Oatley
|
1 |
|
Ogden
|
1 |
|
Ogle
|
3 |
|
Oldfield
|
3 |
|
Oldroyd
|
1 |
|
Oldshore
|
1 |
|
Oliver
|
12 |
|
Ollis
|
2 |
|
Olney
|
1 |
|
Olsen
|
1 |
|
Onslow
|
1 |
|
Onton
|
1 |
|
Oram
|
1 |
|
Orchard
|
1 |
|
Orfice
|
2 |
|
Organ
|
4 |
|
Orme
|
2 |
|
Ormsby
|
2 |
|
Orr
|
5 |
|
Osborn
|
2 |
|
Osborne
|
11 |
|
Oswald
|
1 |
|
Ott
|
1 |
|
Overall
|
2 |
|
Owen
|
1 |
|
Oxenbridge
|
1 |