batman n.

1540s, "a staff used as a weapon," from French bâton "stick, walking stick, staff, club, wand," from Old French baston (12c.) "stick, staff, rod," from Late Latin bastum "stout staff," which probably is of Gaulish origin or else from Greek *baston "support," from bastazein "to lift up, raise, carry." The meaning "staff carried as a symbol of office" is from 1580s; the musical sense of "conductor's wand" is by 1823, from French. Often Englished 17c.-18c. as batoon.