cavolo nero

borrowed from Italian, literally, “black cabbage”. Though Italian cavolo is conventionally translated “cabbage,” the word, with a dependent modifier, actually covers most edible varieties of Brassica oleracea. Cavolo, going back to Late Latin caulus (Latin caulis “stalk of a plant, cabbage”) is apparently dependent on southern dialect forms with preservation of the diphthong and an interposed consonant; the regular central Italian development is represented by Umbrian dialect còlo (see Gerhard Rolhlfs, Grammatica storica della lingua italiana e dei suoi dialetti: Fonetica [Turin: Einaudi, 1966], p. 64)