frankpledge
noun
frank·pledge ˈfraŋk-ˌplej 
: an Anglo-Saxon system under which each adult male member of a tithing was responsible for the good conduct of the others
also : the member himself or the tithing
Word History
Etymology
Middle English frankeplegge, from Anglo-French francplege (probably translation of Middle English friborg peace pledge), from franc free + plege pledge
First Known Use
15th century, in the meaning defined above