"'Hag' is an old word for hedge, incidentally !"

As well as a possible development of "Haw" (meaning hedge) ....

It's also the old word for 'Hag' !

It also used to mean "A boggy area" - so Hagley would be "Boggy Hill"

Another nice one for the folklorists - "An appearance of light and fire on a horse's mane or a man's hair"