It is thought to have started with NAKATOMI no Kamatari (FUJIWARA no Kamatari), who was appointed to Naishin by three successive Emperors, Kotoku, Saimei and Tenchi from 645, was appointed to Naidaijin just before his death.
645年より孝徳天皇・斉明天皇・天智天皇の3代において内臣に任じられた中臣鎌足（藤原鎌足）が死の直前に内大臣に任じられたのが嚆矢とされている。