Couter

The couter (also spelled "cowter") is the defense for the elbow in a piece of plate armour. Initially just a curved piece of metal, as plate armor progressed the couter became an articulated joint.

In fighting reenactment groups such as the Society for Creative Anachronisms, a couter/cowter is often called an elbow cop.

Possibly originates as a nickname for people who made couters. This is a surname/last name.