The Collaborative International Dictionary of English v.0.48:
Chieftaincy \Chief"tain*cy\, Chieftainship \Chief"tain*ship\, n. The rank, dignity, or office of a chieftain. [1913 Webster]WordNet (r) 3.0 (2006):
chieftainship n 1: the position of chieftain [syn: chieftaincy, chieftainship]