Border

Old French bordure — edge of a shield. From border, to border. Originally referred to the decorative edge of a textile or heraldic device before it became a political term for territorial limits.

Militarized and politicized most intensely in the 20th century as nation-states hardened. Before that, borders were porous, contested, and often irrelevant to the people living near them. Today the word carries the full weight of immigration policy, nationalism, and human movement.