Noun
castellum (plural castella or castellums)
(historical) A small Roman detached fort or fortlet used as a watch tower or signal station.
The ancient fortified city was known as Ashdod Yam to the Israelites, Azotos Paralios to the Greeks, and Castellum Beroart to the Crusaders. Source: Internet
The word castle is derived from the Latin word castellum, which is a diminutive of the word castrum, meaning "fortified place". Source: Internet
This particular castellum was thought to be located at the Burcht of Leiden, and the city's name was thought to be derived of the Latin name Lugdunum. Source: Internet