>But the most frequent explanations give like origin le prince Jean 1st, duke of Brabant and marquess of Anvers. Born in 1251 and deceased in 1294, good living and "gai luron" (?), one of his main occupations was to chase the thiefs. After another victory, he gave a commemorative feast. Like the custom required, he gave a speech to his "vassaux" (?).

My French isn't nearly as good as your English but there is an English word "vassal." A vassal is (I hope I have this right) usually a noble whose complete loyalty is pledged to a noble of higher rank.

Could that be the meaning of "vassaux"? It seems to fit in the context of the rest of the story as well.