/ ˈbætmən; NAmE / noun
( pl. -men / -mən; NAmE /) ( BrE ) the personal servant of an officer in the armed forces
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WORD ORIGIN
mid 18th cent. (originally denoting an orderly in charge of the bat horse packhorse which carried the officer's baggage): from Old French bat (from medieval Latin bastum packsaddle) + man .