Cow Down does have an example of a defended Iron Age settlement, and archaeologists have found the remains of round houses there, together with artifacts relating to everyday life, like chalk loom weights.
The hill it tops is the obvious and overriding view from the Neolithic henge near its base. As such I find it tempting to say it had some significance for the people who used and made the henge
You can see a photo of Cow Down from the henge at Deverill Road here.