castellum

Castellum is the diminutive of the Latin castrum (fort, military camp). A castellum was a small fort. The word entered Old English twice, by two different routes. Through the Latin directly, it became ceaster — surviving in place names like Winchester, Manchester, Chester, and Lancaster. Through Norman French chastel, it became castle after 1066. Same Latin word, two English forms, two different centuries of borrowing.

The Norman Conquest made castle a military reality in England. William the Conqueror built castles to hold territory — the Tower of London, Windsor Castle, and over a hundred motte-and-bailey fortifications in his first twenty years. The word castle, in English, is inseparable from the Norman invasion. Before 1066, the English did not build castles. After 1066, they could not escape them.

Castle architecture evolved from simple wooden motte-and-bailey structures to massive stone keeps (1100s), to concentric curtain walls (1200s), to the elaborate trace italienne star forts (1500s) that made medieval castles obsolete. Each stage responded to advances in siege warfare. Gunpowder ended the vertical castle — a high wall is a perfect target for cannon. Fortification went horizontal, and the castle became a residence.

By the eighteenth century, castles were houses. The gothic revival produced castles that were never meant to withstand a siege — Neuschwanstein (1886), built by Ludwig II of Bavaria, has central heating and running water but no murder holes. The word castle survived the transformation. It now means 'a large impressive building that looks old' more often than it means 'a fortified position.'