1676 Boyle New Exp. ii. inPhil. Trans. XI. 800The two surfaces of it gave it some resemblance in point of shape..to a Concavo-Convex Glass.
1727–51 Chambers Cycl. s.v. , Concave,Lenses..concave on one side, and convex on the other, called concavo-convex, or convexo-concave, as the one or the other surface is a portion of a less sphere.
1831 Brewster Optics iv. 27A concavo-convex lens..is a lens one of whose surfaces is concave and the other convex, and in which the two surfaces will not meet though continued.
1858 Geikie Hist. Boulder vi. 98Both the valves are concavo-convex, or arched in the same direction like two saucers..within each other.
ORIGIN: from concave adjective + -o- .