verb trans
to assemble or convene (e.g. troops)
esp of troops: to come together; to congregate
to call the roll of (e.g. a body of troops)
(often + up) to summon (esp courage, nerve) in response to a need
He'd need all the courage he could muster
said esp of troops: to come together; to congregate
[Middle English mustren to show, muster, from Old French monstrer from Latin monstrare to show]