Bible Encyclopedias
Postern

1911 Encyclopedia Britannica

(from 0. Fr. posterne, posterle, Late Lat. posterula, small back-door, posterns, behind), a small gateway in the enceinte of a castle, abbey, &c., from which to issue and enter unobserved. They are often called "sally ports." (See GATE.)

Bibliography Information
Chisholm, Hugh, General Editor. Entry for 'Postern'. 1911 Encyclopedia Britanica. https://www.studylight.org/​encyclopedias/​eng/​bri/​p/postern.html. 1910.