Why is the nut on a viola called a nut?

The term "nut" in the context of a viola (and other string instruments) refers to the small piece of material at the top of the fingerboard, which serves to guide the strings and maintain their spacing. Its name likely derives from the Old English Word "cyning," meaning a small object or piece, which evolved to describe the component that holds the strings in place. The nut plays a crucial role in the instrument's setup, affecting the string height and overall playability.