<P> The word port is ultimately from Latin porta for door . Often the term postern is used synonymously . It can also mean an underground tunnel, or passage (i.e., a secret exit for those besieged). </P> <P> A sally, ultimately derived from Latin salīre (to jump), or "salle" sortie, is a military maneuver, typically during a siege, made by a defending force to harass isolated or vulnerable attackers before retreating to their defenses . Sallies are a common way for besieged forces to reduce the strength and preparedness of a besieging army; a sally port is therefore essentially a door in a castle or city wall, that allows troops to make sallies without compromising the defensive strength of fortifications . </P> <P> Targets for these raids included tools, which defenders could capture and use--and labor - intensive enemy works and equipment, such as trenches, mines, siege engines, and siege towers . Sometimes the defenders also attacked enemy laborers, and stole or destroyed the besiegers' beer and food supplies . </P> <P> An extract from a 19th - century dictionary of military terms describes a sally port thus: </P>

Where did the term sally port come from