Tanistry

Tanistry was a Gaelic system for passing on titles and lands. In this system the Tanist (Irish Tánaiste; Scottish Gaelic Tànaiste; Manx Tanishtagh) was the office of heir-apparent, or second-in-command, among the (royal) Gaelic patrilineal dynasties of Ireland, Scotland and Man, to succeed to the chieftainship or to the kingship.