This book tells the dramatic and often surprising story of the learning of the Irish language by Irish Republican prisoners held in the infamous H-block cells during the bloody political conflict in Northern Ireland. Using research methods and techniques, the author closely analyses the emergence of the Irish language amongst republican prisoners and ex prisoners in Northern Ireland from the 1970s up until the present. This pioneering study shows how the language was used exclusively in parts of the prison, despite the efforts of the prison authorities to suppress the language, and the dramatic impact this had on Irish society. Drawing on interviews with the prisoners, and various other materials, Mac Giolla Chriost shows how these developments gave rise to the popular coinage of the term 'Jailtacht', a deformation of 'Gaeltacht' - the official Irish-speaking districts of the Republic of Ireland, to describe this unique linguistic phenomenon.