• familytreemaker.genealogy.... ;
• He was also known as seigneur de Bourse. The du Bois name is of feudal origin. The name is related to Count de Roussey [c 1110] whose ancestors added this title of du Bois to their patronymic. It is an old name in Neustria, before the time of Rollo.
• The ancient du Bois families were entitled by nobility the right to spell their name with a capital B. In ancient times, two families could not share the same surname without the addition of an agnomen. Neustria is the western part of the Frankish Merovingian Kingdom.

-- http://wc.rootsweb.ancestry.com/cgi-bin/igm.cgi?op=GET&db=chan83&id=I021947