clavis / clavus [ˈkleivəs]
clavis – n. – a key or glossary serving as an aid to interpretation
clavus – n. – 1. corn; 2. a vertical stripe or band of purple on a tunic worn by early Roman senators and narrow by equites as a mark of rank; 3. (Zool.) any of various rounded or finger-like parts or processes as (a) a pointed anal area of the hemelytron of a bug; (b) the club of an insect’s antenna – a vertical component