Overking

the King of Connaught, who was recognized as overking of the island by the rest of the tribe[…]

"They have given me five-and-twenty overkings," protested John, and he at once turned to seek a way of evasion.

The latter asked the aid of Cond the overking, who took up their cause, and a fierce war arose, in which Cond was beaten and compelled to divide Ireland with his rival.

Celtic law, however, explicitly specified that any member of a tribe, including overkings/overqueens of provinces and Druid high priests/priestesses, could be stripped of their legal rights if they failed to execute the legal obligations of their stations.

The difference between a dux bellorum and an overking is not clear, and it may be that the two concepts were elided into a single role.