The Secret Languages of Ireland by R. A. Stewart Macalister
Originally published in 1937, this highly influential book examines the 'secret' languages of Ireland, particularly the Shelta tongue spoken by Irish Travellers, and the various written and spoken forms of Ogham. An appendix at the back allows for the translation of certain English words into a variety of languages, such as Bog-Latin and Bearlagair na Saer. This book will be of value to anyone with an interest in Ireland and the historical languages of its people.