Saxon "offa" means "open", while "uffern" is oven, inferno, volcano. (The village is referred to in the Domesday Book as Uffintone. [A. D. Mills, "A Dictionary of English Place-Names," Oxford University Press, 1991]).
Dragon Hill and the horned beast seem to be linked with such expressions. The WH Hill itself is shaped like a vent with the animals seeming to leap upwards on the summit.
Is it possible that the Otherworld lay at the foot of the hill and there were funerals held in the top enclosure? There are no objects found there to indicate a military use of the site, but it lies on the border of 2 Celtic lands, perhaps suggesting the remote location of the Otherworld and passage there at death.
Maybe the chalk beast is the daughter of the volcano-living Echidna dragon, the goat-horned lion known as Beaufort Yale, who was the Chimera connected with a volcanic vent south of Celtic Galatia in Asia Minor...that's a long story....