meniscus

The story

1. Proto-Indo-European*med-
2. Proto-Indo-European*meh₁-?
3. Proto-Indo-European*mḗh₁n̥s
4. Proto-Hellenic*méns
5. Ancient Greekμείς (meís)
6. Ancient Greekμηνῐ́σκος (mēnĭ́skos)
7. English todaymeniscus

From Ancient Greek μηνίσκος (mēnískos, “crescent”), from μήνη (mḗnē, “moon”). Piecewise doublet of moonish.

First known use, by meaning

• from 17th c. A crescent moon, or an object shaped like it.
• from 17th c. A lens which is convex on one side and concave on the other, being crescent-shaped in cross-section.
• from 19th c. The curved surface of liquids in tubes, whether concave or convex, caused by the surface tension of the liquid.
• from 19th c. Either of two parts of the human knee that provide structural integrity to the knee when it undergoes tension and torsion.