Of or pertaining to the hip; in the region of, or affecting, the hip; ischial; ischiatic; as, the sciatic nerve, sciatic pains.
adjective, Greek ischion = hip-joint. Ischiadikos meant pertaining to the ischium or hip - later changed to sciatic. (The ischium earns its name because it forms 2/5 of the acetabulum, whereas the ilium contributes 2/5, and the pubis only 1/5). The sciatic nerve lies on the ischium.
of or relating to the ischium (or the part of the hipbone containing it); "sciatic nerve"