bailey (n.) Look up bailey at Dictionary.com
early 14c., baylle, "wall enclosing an outer court" of a castle, etc. (c. 1200 in Anglo-Latin), a variant of bail, from Old French bail "stake, palisade, brace," which is of unknown origin, perhaps ultimately connected to Latin bacula "sticks," on notion of "stakes, palisade fence."

The word was later extended to mean the outer court itself. Hence Old Bailey, seat of Central Criminal Court in London, 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).