tanist

1. (historical) The heir presumptive to the chieftainship or kingship of a Celtic clan in ancient Ireland, Scotland or Mann.Examples: "Lover, for her love he prowled with colonel Richard Burke, tanist of his sept, under the walls of Clerkenwell and, crouching, saw a flame of vengeance hurl them upward in the fog."; "In 1570 Dermot died at 'his own house' of Castle Inch. His brother and tanist, Cormac Mac Teige (fourteenth Lord), succeeded him (Ó Murchadha, p. 16)."; "As a result of the universal introduction of the English common law, therefore, the original tanist acquired a common law title to the disputed land 'without grant or confirmation of the conqueror'."historical