fībula

Fībula is the Latin word for a brooch or clasp — the ancient equivalent of a safety pin, used to fasten garments. The bone was named by analogy: the fibula and tibia together were seen as resembling a fibula-clasp, with the fibula as the pin and the tibia as the bar it clasps against. The metaphor is visual. The thin, straight fibula running alongside the broad tibia does resemble a pin alongside a bar.

Roman fibulae — the brooches — were everywhere. They fastened togas, cloaks, and tunics. They were made of bronze, iron, silver, and gold. Archaeologists have found thousands of them across the Roman Empire. The bone that shares their name is equally everywhere: every human has two fibulae, one in each lower leg. But unlike the tibia, the fibula bears almost no weight. It is a structural attachment point for muscles and ligaments, not a load-bearing column.

The fibula is the bone most commonly used for bone grafts because it can be removed without significantly affecting leg function. Surgeons discovered this in the 20th century: take out a section of fibula, and the patient can still walk. The bone that bears no weight turns out to be a spare part. The brooch-pin is also a donor bone.

English adopted fibula in the late 17th century from Latin anatomy. There is no everyday English name for the fibula the way there is for the tibia (shinbone). Most people do not know its name because most people do not know it exists. The tibia gets the bruises. The fibula works in silence.