Charlemangne’s 782 Capitulatio de partibus Saxoniae prescribed laws for Saxons which included being baptized. Failure to do so was punishable by death. “If any one of the race of the Saxons hereafter concealed among them shall have wished to hide himself unbaptized, and shall have scorned to come to baptism and shall have wished to remain a pagan, let him be punished by death”. It's likely that these crosses were worn as an indication of that acceptance and by extension, submission to Carolingian rule.