Is it ensure, insure, or assure?
early 13c., from Anglo-French treson, from Old French traison (11c.; Modern French trahison), from Latin traditionem (nominative traditio) "a handing over, delivery, surrender" (see tradition). Old French form influenced by the verb trair "betray." In old English law, high treason is violation by a subject of his allegiance to his sovereign or to the state; distinguished from petit treason, treason against a subject, such as murder of a master by his servant.