The edge of a thing, drawn so the edge can be seen. It marks where something ends without saying what lies beyond.
Old French bordure, from a Frankish/Germanic root *bord- (edge, rim), related to the same family as 'board'; a border was first a decorative or protective edge before it marked a boundary line.
The edge of a thing, drawn so the edge itself can be seen — it marks where something ends without making any claim about what lies past it.