A pledge or surety for the good behavior of freemen, -- each freeman who was a member of an ancient decennary, tithing, or friborg, in England, being a pledge for the good conduct of the others, for the preservation of the public peace; a free surety.
Bouvier. [
1913 Webster]
"The servants of the crown were not, as now, bound in frankpledge for each other."
[1913 Webster]