锥 (zhuī) is an awl — the pointed metal tool — and by extension anything that tapers to a point. Pair it with
形 "shape" and you get "awl-shape," i.e., conical. Same character family:
圆锥 (yuánzhuī, geometric cone),
锥子 (an awl/pricker),
锥度 (taper/conicity).
