1. A silhouette is the outline of a dark shape with a bright light or pale background behind it.
2. The silhouette of something is the outline that it has, which often helps you to recognize it.
(Collins Cobuild)
From Étienne de Silhouette, French finance minister in 1757, who loved the art of making cut-out figures that was very popular in France from 1730.
It’s amazing what you learn by watching the Antiques Road Show.