[This is a fast-access FAQ excerpt.]
This expression, meaning "accept the unpleasant consequences", is
first recorded in the U.S. around 1850. It may derive from musical
theatre: a nervous actor would have to summon all his courage to
face the audience across the orchestra pit. Or it may be one of
three military references: an infantryman taking his place in the
line of assembly; a cavalier keeping his restive horse still while
the band starts to play; or a soldier being drummed out of his
regiment.