Is it ensure, insure, or assure?
Old English here-geatwe (plural) "military equipment, army-gear," from here "army" (see harry). An Anglo-Saxon service of weapons, loaned by the lord to his retainer and repayable to him upon the retainer's death; transferred by 13c. to a feudal due upon the death of a tenant, payable to his lord in beasts.
in European feudal society, the right of the lord to seize his tenant's best beast or other chattel on the tenant's death. The right grew out of the custom under which the lord lent horses and armour to those of his tenants who served him in battle. When a tenant died, the horse and equipment were returned to the lord. When the tenant became responsible for providing his own equipment, the lord claimed the right to heriot. There were various types of heriot. Heriot service was an incident of both free and unfree land tenure, i.e., both unfree, or villein, tenants and free tenants were subject to the feudal lord's right of heriot. A tenant could make provision for the payment of heriot in his will, but if he died in battle no heriot was required