Trendle Ring (or Trundle Ring) is an Iron Age earthwork on the Quantock Hills near Bicknoller in Somerset, England. The word trendle means circle, so it is a tautological place name.
The so-called hill fort has several features that make it more likely to be an animal enclosure, rather than a defended settlement:

single rampart with ditch
simple opening for an entrance
situated on the slope of a hill
the hill rises 130 m above the ring
the area is only 0.7 ha