Marshal is a term used in several official titles in various branches of society. As marshals became trusted members of the courts of Medieval Europe, the title grew in reputation. During the last few centuries, it has been used for elevated offices, such as in military rank and civilian law enforcement.
In most countries, the rank of Marshal is the highest Army rank (equivalent to a five-star General of the Army in the United States).
"Marshal" is an ancient loanword from Norman French (cf. modern French maréchal), which in turn is borrowed from Old Frankish *marhskalk (="stable boy, keeper, servant"), being still evident in Middle Dutch maerscalc, marscal, and in modern Dutch maarschalk (="military chief commander"; the meaning influenced by the French use).
It is cognate with Old High German mar(ah)-scalc "id.", modern German (Feld-)Marschall (="military chief commander"; the meaning again influenced by the French use).
It originally and literally meant "horse servant", from Germanic *marha- "horse" (cf. English mare and modern German Mähre, meaning "horse of bad quality") and *skalk- "servant" (cf. Old Engl. scealc "servant, soldier" and outdated German Schalk, meaning "high-ranking servant"). This "horse servant" origin is retained in the current French name for farrier: maréchal-ferrant.
The late Roman and Byzantine title of comes stabuli ("count of the stables") was a calque of the Germanic, which became Old French con(n)estable and modern connétable, and, borrowed from the Old French, the English word "constable". Finally, in Byzantium, a marshal with elevated authority, notably a borderlands military command, was also known as an exarch.
Field Marshal
In many countries, the rank of marshal, cf. field marshal, is the highest army rank, outranking other general officers. The equivalent navy rank is often admiral of the fleet or grand admiral.
Marshals are typically, but not exclusively, appointed only in wartime. In many countries, especially in Europe, the special symbol of a marshal is a baton, and their insignia often incorporate batons.