The origin of the term dates to the early Middle Ages, originally meaning the keeper of the king's horses (from Old German "Marh-scalc" = "horse-servant"), from the time of the early Frankish kings; words originally meaning "servant" were sometimes used to mean "subordinate official" or similar. The exact wording of the titles used by field marshals varies: examples include "marshal" and "field marshal general". The air force equivalent in Commonwealth and many Middle Eastern air forces is marshal of the air force (not to be confused with air marshal). Navies, which usually do not use the nomenclature employed by armies or air forces, use titles such as "fleet admiral," "grand admiral" or "admiral of the fleet" for the equivalent rank. The traditional attribute distinguishing a field marshal is a baton. The baton nowadays is purely ornamental, and as such may be richly decorated. That said, it is not necessary for the insignia to be a baton (Such is the case in Russia post-1991 and the former Soviet Union, which use a jewelled star referred to as a Marshal's star).