You've heard of moats and drawbridges, but barbicans may be unfamiliar. Those stone outworks stand in front of the gate of a castle or bridge and historically helped prevent invaders from gaining access to the main entryway. Up to a point, the case for the history of the word barbican is well fortified. It is clear that English speakers seized the term from the Anglo-French barbecane, which in turn had been taken from the Medieval Latin barbacana (both of those words had the same meaning as the modern word). The etymological path crumbles from there, however. Some speculate that the ultimate ancestor of barbican might lie in a Persian phrase meaning "house on the wall," but that speculation has never been proven.
Word History
Etymology
Middle English, from Anglo-French barbecane, from Medieval Latin barbacana