1800, "chromium," from French chrome, the name proposed by Fourcroy and Haüy for a new element, from Greek khrōma "color" (see chroma); so called because it makes colorful compounds. The metallic element had been isolated 1798 by French chemist Louis Nicolas Vauquelin, who named it chrome. It is now known as chromium (q.v.).
Chrome continued in commercial use in English for "chrome steel" (steel with 2 percent or so chrome) after the chemical name was changed internationally. As a short form of chromium plating it dates from 1937. Related: Chromic.
"having or tinted with several or many colors," 1816, from French polychrome, from Latinized form of Greek polykhrōmos (also polykhrōmatos) "many-colored" (see poly- + chrome). As a noun from 1800, "work of art decorated in several colors;" by 1838 as "a fluorescent substance forming prismatic crystals." Related: Polychromic; polychromatic; polychromate.