Translated from the Welsh the name Caerfai, which is given to the bay and the fort, means fort bay. It’s another one of those strange Welsh/English naming things, because the fort’s name refers to the bay that was named after the fort (if you see what I mean). Things have very nearly come full circle.
As well as being known as Caerfai Camp or Fort, the site is also known as Penpleidiau Camp, after the small island that lies to the south of it.