Castel-burg

According to the Old English Dictionary:

castel-burg

a fortified place ? :-- Hec sunt confinia . . . inde in montem susibrem urbs antiqua et postea bi þǽre aldan cestelbyrig on nunnena beorgas, C. D. B. i. 205, 8. [Ne moste na mon cumen wiðinne þon castelburi, Laym. 6714.] castel-burg