caboche

Cabochon comes from the Old French caboche, meaning 'head' or 'knob,' itself from the Latin caput (head). The diminutive form cabochon — 'little head' — described the rounded, polished shape given to gemstones before faceting technology existed. For most of human history, this was the only way to cut a stone: grind it smooth, polish it into a dome, and set it in metal.

Faceting — cutting flat surfaces at precise angles to maximize light refraction — did not emerge until the late medieval period. The first rudimentary facets appeared in the 1300s, and the brilliant cut was not developed until 1919 by Marcel Tolkowsky in Antwerp. Before faceting, every sapphire, every ruby, every emerald was a cabochon. The crown jewels of every medieval European monarchy were set with cabochon-cut stones.

Certain stones are still cut en cabochon because faceting would destroy their optical effects. Star sapphires display asterism — a six-pointed star of light that appears only on a domed surface. Cat's eye chrysoberyl shows chatoyancy — a moving band of light — only as a cabochon. Opals reveal their play of color best when rounded. The old cut survives because it does something the new cut cannot.

The word entered English in the 1570s. Jewelers today use it both as a noun — 'a cabochon' — and as an adjective — 'cut en cabochon.' The oldest cutting method in gemology is named after a head. The newest, the brilliant cut, is named after light. The history of gemstones sits in the distance between those two metaphors.