sussex and other places like essex and middlesex have some suffix that signifies “town” or something, presumably in anglo-saxon

https://www.youtube.com/watch?v=uYNzqgU7na4

The name Essex originates in the Anglo-Saxon period of the Early Middle Ages and has its root in the Anglo-Saxon (Old English) name Ēastseaxe (‘East Saxons’), the eastern kingdom of the Saxons who had come from the continent and settled in Britain.

https://en.wikipedia.org/wiki/Essex