an ancient custom in Ireland, dating from tribal times, which regulated the succession to power of clan chieftains and kings. Under tanistry, the successor, or tanist, to the king or chieftain was chosen while the ruler was still alive; he was elected from among the representatives of the elite family having the right to claim succession. Originally, all freemen had the right to participate in the selection of the tanist. With the development of feudalization, only the clan elite enjoyed the privilege. The custom of tanistry continued until the early 17th century.