This most interesting surname is the Anglicized form of the Gaelic surname "O'Rioghbhardain", a numerous sept found exclusively in Munster. The Gaelic name itself is composed of the Gaelic prefix "O", male descendant of, and "Rioghbhardan", a byname composed of the Gaelic elements "riogh", royal and "bhard", a bard, poet. The surname is also found as Rearden and O'Riordan. The sept of O'Riordan originated in Co. Tipperary, and migrated to Co. Cork at such an early date they can be regarded as belonging to that county, where they are far more numerous than anywhere else. They gave their name to Ballyreardon in East Cork, which indicates that they were influential in this area, where they were followers of the lords of Muskerry. Several Co. Cork O'Riordans appear as Irish soldiers in the 17th Century. MacFirbis mentions a family of "O'Riordan", who were historians of Eile, but little is known of these. A branch of the O'Riordans, from Derryroe, Cork, settled in Nates in 1753 and became Peers of France. Michael Riordan, aged 22 yrs., was an Irish famine immigrant, who left Cork on the "Liberty" for New York on May 21st 1846. A Coat of Arms was granted to the family depicting quarterly: first and fourth, red out of clouds in the sinister side a dexter arm fessways proper, holding a dagger in pale silver pommel and hilt gold; second and third, silver, a lion rampant red against a tree in the dexter couped proper. The first recorded spelling of the family name is shown to be that of Domhnall O' Rioghthardain, which was dated 1658, in the "All Ireland Census", during the reign of Richard Cromwell, known as "The Lord Protector", 1658 - 1659. Surnames became necessary when governments introduced personal taxation. In England this was known as Poll Tax. Throughout the centuries, surnames in every country have continued to "develop" often leading to astonishing variants of the original spelling.