Which preposition to use with ealdorman

in Occurrences 2%

In the primitive process of aggregation, the shire or gau, governed by its witenagemote or "meeting of wise men," and by its chief magistrate who was called ealdorman in time of peace and heretoga, "army-leader," dux, or duke, in time of war,the shire, I say, in this form, is the largest and most complex political body we find previous to the formation of kingdoms and nations.

of Occurrences 2%

The chief magistrate was not the ealdorman of early English history, but the rex or basileus who combined in himself the functions of king, general, and priest.

over Occurrences 1%

His son Edward and his son-in-law Ethelred, whom he had set as ealdorman over what remained of Mercia, showed themselves as skilful and active as the King.

Which preposition to use with  ealdorman