What is the X in X-mas?
1872, from Latin catenarius "relating to a chain," from catenanus "chained, fettered," from catena "chain, fetter, shackle" (see chain (n.)). As a noun from 1788 in mathematics. Related: Catenarian.
in mathematics, a curve that describes the shape of a flexible hanging chain or cable-the name derives from the Latin catenaria ("chain"). Any freely hanging cable or string assumes this shape, also called a chainette, if the body is of uniform mass per unit of length and is acted upon solely by gravity.