Tonneau (pronounced ta’-no) is an archaic term (originally from the French, roughly meaning cask, container, or cover) for an open rear passenger compartment on an automobile and, by extension, a body style incorporating such a compartment. Most tonneaus were fixed in place as an optional element at purchase, but some could be removed as on the Crestmobile. Early tonneaus had a rear-facing hinged door as a rule, but single- or dual side doors were soon introduced.