Sage comes directly from the Latin sapere, to know, shared by both the English word for wisdom and the herb long associated with clear-headed judgment. The name states its meaning plainly -- discernment named outright rather than implied through symbol or story.
He that asserts things that can never be proved by experience is deceived and ambitious, but thus it always happens, those that are most ignorant of Art delights to boast of doing things different or wonderful. - Cardan Girolamo (1501-1576)