It's an old Irish phrase that translates to, "We Ourselves", which is appropriate given the political agenda tied to it.

Irish republican party - a nationalist Irish republican party founded in 1905. [Early 20th century. < Irish sinn féin "we ourselves"] http://encarta.msn.com/encnet/features/dictionary/DictionaryResults.aspx?refid=1861734942 Etymology: Irish, "(we) ourselves" (strictly) Sinn Féin - An Irish political party committed to the reunification of Ireland. http://en.wiktionary.org/wiki/Sinn_Fein Sinn Féin (pronounced /ˌʃɪnˈfeɪn/ in English, IPA: [ʃiːɲ fʲeːnʲ] in Irish) is a name used by a series of Irish political movements of the 20th century, each of which claimed sole descent from the original party established by Arthur Griffith in 1905. The name translates as "ourselves" or "we ourselves", though it has often been rendered as "ourselves alone". In modern politics, the name almost always refers to the political party dedicated to Irish Republicanism that is often seen as the political front of the Provisional Irish Republican Army. The party emerged from a 1970 fissure in the Irish republican movement. Its current leader is Gerry Adams, a controversial figure in Irish politics. Sinn Féin’s most notable feature is its Irish Nationalism, but it is also a left-wing organisation, espousing socialist views with support for greatly increased public spending on the poor, as well as universal healthcare. It is established in both the Republic of Ireland (with four seats out of 166 in Dáil Éireann and one seat in Seanad Éireann) and Northern Ireland (with 27 seats out of 108, the largest Irish nationalist party in the Northern Ireland Assembly). Having been in opposition to the previous governments of the Republic of Ireland, the party have already declared they will not support the new Fianna Fáil/PD/Green Party cabinet that has been formed. http://en.wikipedia.org/wiki/Sinn_Fein