vertex

Vertex entered late Middle English from Latin vertex, meaning both 'whirl, eddy' and 'top, crown, peak, summit.' It is a doublet of vortex, meaning the two words descend from the same Latin source.

Latin vertex already carried both senses — the swirling motion and the highest point — and English kept the summit sense, using vertex for peaks, crowns, and later mathematical points.

Vertex shares its Latin root with vortex, so a mountain's tip and a swirling whirlpool are, etymologically, the same idea seen from different angles.