Ó Sirideáin is the original Irish Gaelic form of the surname Sheridan. Derived from the Old Irish personal name Sirideán, the name is believed to mean "searcher" or "inquisitor." The prefix Ó indicates "descendant of," so the surname traditionally denoted a descendant of a male ancestor named Sirideán.
Historically, the Ó Sirideáin family belonged to the ancient province of Connacht in western Ireland. They were a minor Gaelic sept whose genealogical traditions were recorded in compilations such as the Annals of the Four Masters and the Genealogies of the Uí Briúin, the ruling dynasty of the region. In the 17th century, during the destruction of the Gaelic order under the Cromwellian conquest and the subsequent Penal Laws, many bearers anglicized their name to Sheridan, a common pattern among Irish Catholic gentry to avoid persecution.
One of the most famous descendants of the Ò Sirideáin line, bearing the anglicized form, is Thomas Sheridan (1687–1738), an Irish Protestant clergyman and friend of Jonathan Swift, not to be confused with his grandson Richard Brinsley Sheridan, the celebrated playwright and politician. The surname also appears canonicially in works of literature, notably in the characterization of Mrs. Malaprop from Sheridan's The Rivals (1775).
Today, the original Gaelic form remains rare, kept alive mainly in historical records and individual revivals in the Gaeltachtaí and by families proud of their pre-Anglicization heritage. Variants of the name outside of the Sheridan form include O'Sheridan and the alternate graphemes O'Sheridan and O'Sireadáin.
- Meaning: "descendant of the searcher"
- Origin: Irish Gaelic from the personal name Sirideán
- Type: Surname (patronymic)
- Usage regions: Mostly Connacht, Ireland, but the anglicized form is now widespread