Is it ensure, insure, or assure?
"wall enclosing an outer court," early 14c. (c.1200 in Anglo-Latin), baylle, variant of bail, from Old French bail "stake, palisade, brace," of unknown origin, perhaps ultimately connected to Latin bacula "sticks," on notion of "stakes, palisade fence." Old Bailey, seat of Central Criminal Court in London, was so called because it stood within the ancient bailey of the city wall. The surname Bailey usually is from Old French bailli, a later form of baillif (see bailiff).