English castles, much like most other European castles, were named after the city/town they were built in/near - often by the noble who owned them. Even if your placenames are non-English, this naming method would still work, I believe.

Castles typically get their names from four primary sources: geography, the founding family, military purpose, or local folklore. Many are named after the town or strategic feature they guard, such as Warwick Castle (situated in Warwick) or Caernarfon (meaning "fort in Arfon"). The word "castle" itself comes from the Latin castellum, a diminutive of castrum (fortified place). Some carry the name of the noble who commissioned them, or an evolved version of a previous structure, like Windsor Castle, which derives from the Old English Windlesora (winch by the riverbank). In other cases, descriptive nicknames stuck; The Tower of London refers to the central White Tower, while Castello Estense in Italy is named after the Este family. Occasionally, names reflect a castle's physical traits, such as Château Gaillard ("Saucy Castle"), named by Richard the Lionheart for its defiant strength. In 2026, many of these names are essentially brand identifiers for heritage sites, but they remain deeply rooted in the medieval feudal system where a castle was not just a home, but a "statement of power" in the landscape.