Sinn Féin roughly translates as "Ourselves", "Ourselves Alone" or "Our own selves".
Originally a political party founded by Arthur Griffith to promote the objectives of Dual Monarchy and self sufficiency for Ireland. Although it had no direct involvement with the 1916 Rising, the British termed this rebellion a "Sinn Féin Rebellion", thus increasing the party's support within Ireland dramatically, leading to their electoral victory in the 1918 general election.
From this point, until the Irish Civil War of 1922, Sinn Féin was generally the party of those who supported the cause of Irish independence.
Since the end of the Civil War, Sinn Féin has been adopted by the various incarnations of the IRA as the name of their political wing. Since the ceasefire of 1997, today's Sinn Féin have come to resemble more closely a genuine political party, although not everybody is convinced. The policies of today's Sinn Féin bear little resemblence to those of its founders, but they use the name on the basis that they claim to uphold the principles contained in the 1916 proclamation of the Irish republic.