Why is the ninth month called September?
early 13c. as a surname; mid-13c. as "high officer of the royal court;" from Old French mareschal "commanding officer of an army; officer in charge of a household" (Modern French maréchal), originally "stable officer, horse tender, groom" (Frankish Latin mariscaluis) from Frankish *marhskalk or a similar Germanic word, literally "horse-servant" (cf. Old High German marahscalc "groom," Middle Dutch maerschalc), from Proto-Germanic *markhaz "horse" (see mare (1)) + *skalkaz "servant" (cf. Old English scealc "servant, retainer, member of a crew," Dutch schalk "rogue, wag," Gothic skalks "servant").
Cognate with Old English horsþegn. From c.1300 as "stable officer;" early 14c. as "military commander, general in the army." For development history, cf. constable. Also from Germanic are Italian scalco "steward," Spanish mariscal "marshal."
early 15c., "to tend (horses)," from marshal (n.). Meaning "to arrange, place in order" is from mid-15c.; that of "to arrange for fighting" is from mid-15c. Figurative use by 1690s. Related: Marshaled; marshaling.