| # | Name | Origin | Meaning | Gender | |
|---|---|---|---|---|---|
| 1501 | Oonagh | Irish | Lamb. Can also be an Irish variant of Latin Una': One. | F | |
| 1502 | Oran | Irish | Pale green. | M | |
| 1503 | Orghlaith | Irish | Golden. | F | |
| 1504 | Orla | Irish | Golden. | F | |
| 1505 | Orlaith | Irish | Golden. | F | |
| 1506 | Orlaithe | Irish | Golden. | F | |
| 1507 | Ossian | Irish | Fawn. | M | |
| 1508 | Paddy | Irish | Diminutive of Patrick: noble. Paddy is also sometimes used as a slang term for Irishman or for a temper tantrum. | M | |
| 1509 | Padraic | Irish | Patrician; noble. Form of Patrick. | M | |
| 1510 | Padraig | Irish | Noble. | M | |
| 1511 | Padraigin | Irish | Noble. | F | |
| 1512 | Padriac | Irish | Noble. | M | |
| 1513 | Padric | Irish | Patrician; noble. Form of Patrick. | M | |
| 1514 | Parnel | Irish | Nineteenth-century Irish Nationalist Charles Parnell. | M | |
| 1515 | Parnell | Irish | Nineteenth-century Irish Nationalist Charles Parnell. | M | |
| 1516 | Pat | Irish | Patrician; noble. Abbreviation of Patrick. | M | |
| 1517 | Patrick | Irish | Patrician; noble. Romans society was divided into plebeians: (commoners) and patricians: (aristocrats). Saint Patrick - patron saint of Ireland. | M | |
| 1518 | Payton | Irish | Patrician; noble. Form of Patrick. | M | |
| 1519 | Pearce | Irish | Form of Piers from Peter. | M | |
| 1520 | Pearson | Irish | Form of Piers from Peter. | M | |