Calf bone: Familiar name for the fibula, the lateral (outside) and smaller of the two long bones in the lower leg. The other bone in the lower leg is the tibia. The tibia bears weight; the fibula does not.
The word "fibula" comes from the Latin meaning clasp or brooch. The fibula was likened to a clasp attaching it to the tibia to form a brooch.
The word "calf" comes through the Anglo-Saxon, it is thought, from the Indo-European ""gelbh" meaning "to bunch up", as do the muscles of the calf.