Cockscomb is Celosia, a genus of the amaranth family native to tropical Africa, Asia and the Americas, grown almost everywhere in the warm world both as an ornamental and, in west Africa and southeast Asia, as a leaf vegetable. The garden forms fall into two groups. The cristata or crested kinds carry a fasciated inflorescence, a growing point flattened and folded into a dense velvety brain-like ridge that does genuinely resemble the comb of a cockerel; the plumosa kinds keep the flowers in upright feathery spires. The genus name comes from the Greek keleos, burning, for the scarlet, orange and magenta of the typical forms. The crested shape is a developmental abnormality that has been selected and fixed by gardeners rather than a normal wild form, which makes the plant a small and vivid example of how ornamental horticulture works.
In Nigeria the young leaves of Celosia argentea are a staple vegetable known in Yoruba as soko yokoto, roughly make the husband fat and happy, cooked into a rich stew and eaten far more widely there as everyday food than as an ornamental, a use standing in real contrast to the crested, brain-like cristata forms grown purely for show in Western gardens. The same plant appears as a leaf vegetable in parts of Southeast Asia and China, so that a single genus does double duty across the world, prized in one region chiefly for its startling ornamental shape and in another simply as a nutritious, fast-growing green.
Sources Plants of the World OnlineRoyal Botanic Gardens, Kew with Encyclopaedia Britannica (online academic reference)Encyclopaedia Britannica editors