trench [LME] This comes via Old French trenche ‘cutting, cut, ditch’ as a noun and trenchier as a verb, which go back to Latin truncare ‘to cut off’. Trenchant [ME] is from the same source and in the past was used literally of a sharp edge as well as of incisive language. Tranche [LME] is simply the modern French for ‘a part, slice’ adopted directly into English and used in a literal sense from about 1500, but in economics for an instalment of a loan etc. only from the 1930s. A trench coat [E20th] get its name because it was designed for use in the trenches of the First World War.