1560s, "the point opposite the base in geometry," from Latin vertex "highest point," literally "the turning point," originally "whirling column, whirlpool," from vertere "to turn" (see versus). Meaning "highest point of anything" is first attested 1641.
vertex ver·tex (vûr'těks')
n. pl. ver·tex·es or ver·ti·ces (-tĭ-sēz')
The highest point; the apex.
The topmost point of the vault of the skull; the crown of the head.
The portion of the fetal head bounded by the planes of the trachelobregmatic and biparietal diameters, with the posterior fontanel at the apex.