1550s "massive monumental stone structure of polygonl plan, the sides of which slope in planes to a common apex," also a geometrical solid resembling this, (earlier in Latin form piramis, late 14c., or nativized in Middle English as piram), from French pyramide (Old French piramide "obelisk, stela," 12c.), from Latin pyramides, plural of pyramis "one of the pyramids of Egypt," from Greek pyramis (plural pyramides) "a pyramid," which is apparently an alteration of Egyptian pimar "pyramid."
Greek pyramis also meant "kind of cake of roasted wheat-grains preserved in honey," and in this sense is said to derive from pyros "wheat" on the model of sesamis. According to some old sources the Egyptian pyramids were so called from their resemblance to the form of the cake, but Beekes points out that "the form of the cake is actually unknown."
Figurative of anything with a broad base and a small tip. Financial senses are by 1911. Related: Pyramidal (late 14c., piramidal).