Is it ensure, insure, or assure?
Old English becweðan "to say, speak to, exhort, blame," also "leave by will;" from be- + cweðan "to say," from Proto-Germanic *kwithan, from PIE *gwet- "to say, speak."
Original sense of "say, utter" died out 13c., leaving legal sense of "transfer by will." Closely related to bequest. "An old word kept alive in wills" [OED 1st ed.]. Old English bequeðere meant "interpreter, translator." Related: Bequeathed; bequeathing.