lens

Where does the word "lens" come from? It comes from Latin lens, and was adopted directly into English (1690s).

Lens’s story begins in Latin: lens meant “a lentil.” Literally a lentil, since early ground-glass optical lenses resembled the flattened seed's shape. It reached English by 1690s as lens. Latin 'lentil', since a double-convex lens is lentil-shaped. Today, lens means a curved piece of transparent material used to focus or diverge light.

1. Stage 1 · Latin · ancient lens "a lentil", literally a lentil, since early ground-glass optical lenses resembled the flattened seed's shape.
2. Stage 2 · English · 1690s lens "a curved piece of glass used to focus light", Latin 'lentil', since a double-convex lens is lentil-shaped.