I never thought to look up the etymology of lens before, but I was pleasantly surprised to find that its origin was a lot more interesting than I would have expected. The word was first used in a 1693 treatise on solar eclipses, in reference to the part of a telescope. It was borrowed from Medieval Latin lens, but in earlier Latin it had the meaning of "lentil". The connection was apparently that the convex shape of the glass looks similar to the curvature of the legume. As you might have guessed, we also got our word lentil from the Latin noun, through the diminutive lenticula and French lentille. Finally, lens probably comes from a non-Indo-European language, because there are clear cognates in other IE languages that do not follow the normal rules of sound change. That's unsurprising, since it's pretty common for agricultural names to come from the people previously inhabiting the land.
Hello! I'm Adam Aleksic, a sophomore studying government and linguistics at Harvard University, where I co-founded the Harvard Undergraduate Linguistics Society. In addition to etymology, I also really enjoy politics, vexillology, geography, board games, conlanging, and law.