The AI-powered English dictionary
usually uncountable, plural tanistries
(historical) A form of tenure, in ancient Scotland and Ireland, whereby succession was passed to an elected member of the same extended family. quotations
They also have to make allowance, in place of primogeniture, for the practice of tanistry, that is, the naming of a successor who was not necessarily the ruler's son.
2011, Norman Davies, Vanished Kingdoms, Penguin, published 2012, page 50