meniscus (n.)

"a crescent or crescent-shaped body," 1690s in reference to lenses convex on one side, concave on the other, and thicker in the middle; c. 1812 in reference to liquid surfaces, Modern Latin meniscus, from Greek meniskos "lunar crescent," diminutive of mene "moon" (see moon (n.)). Related: Meniscoid; mensicoidal; mensical; mensicate.