baluster (n.)

also balluster, "support for a railing" (commonly one that swells outward at some point), c. 1600, from French balustre (16c.), from Italian balaustro "small pillar," said to be from balausta "flower of the wild pomegranate," from Greek balaustion (which is perhaps of Semitic origin; compare Aramaic balatz "flower of the wild pomegranate"). The uprights had lyre-like double curves, which resembled the half-opened pomegranate flower.