The term 'Pear-Shaped Fiddle' is a reference to the musical instrument known as the rebec, which is a bowed string instrument that was popular in Europe during the Middle Ages and Renaissance periods. The rebec has a pear-shaped body and typically has three strings. It is believed to have originated in the Middle East and was brought to Europe by the Moors. The rebec is still used today in folk music and is sometimes referred to as a 'medieval fiddle'.