Fibula, directly from the Latin fibula, a Roman clothing clasp or brooch: in essence, an ancient safety pin. The fibula and the tibia of the leg, when taken together, represent the clasp with the much thinner fibula representing the clasp's pin.

A Roman fibula (clasp) ca. 3rd-4th century A.D. www.edgarlowen.com	Anterior view of the fibula and tibia. The fibula, on the left, is the lateral (outer) bone of the lower leg. From: Andreae Vesalius, De Humani Corporis Fabrica, 1543, p.136

Fibula was not used in anatomy until it was introduced by Vesalius in the 16th century. The Greek name for the bone, perone (=pin), is the root word for such fibula-related structures as the peroneus muscles and the peroneal nerves (the terms fibularis and fibular are now favored over peroneus and peroneal by textbook writers, though the Terminologia Anatomica still lists both sets of terms).

It is not uncommon for the bone to be misspelled as "fibia" by beginning students and for whom this mnemonic would be useful: FibuLa, Lateral bone of the Lower Leg.

Unrelated but interesting: In the early days of the Roman Empire the prepuces (foreskins) of actors and singers were pinned with fibulae (the clasps) in the belief that sexual intercourse damaged the voice. This practice was eventually ended, I suppose when it was noticed that many prospective actors and singers were choosing less risky career paths.