The city's name, first recorded in the Domesday Book in 1086 as Loncastre, where "Lon" refers to the River Lune, and "castre", from the Old English cæster and Latin castrum for "fort", refers to the Roman fort which stood at the site.Roman baths were discovered in 1812 and can be seen near the junction of Bridge Lane and Church Street.A permanent military presence was established in the town with the completion of Bowerham Barracks in 1880.
Lancaster Castle, partly built in the 13th century and enlarged by Elizabeth I, stands on the site of a Roman garrison.
Despite a lack of documentation from the period, it is likely that Lancaster was still inhabited.
Lancaster was on the fringes of the kingdoms of Mercia and Northumbria, and over time, control may have changed from one to the other.
There was presumably a bath-house belonging to the 4th-century fort.
They incorporated a re-used inscription of the Gallic Emperor Postumus, dating from AD 262 to 266.