Etymology

Noun

1. Gathering.
   1. An assemblage or display; a gathering, collection of people or things.
      • 1743, Joseph Steele & Richard Addison, The Lucubrations of Isaac Bickerstaff, Esq.:

        She seems to hear the Repetition of his Mens Names with Admiration; and waits only to answer him with as false a Muster of Lovers.

   2. An assembling or review of troops, as for parade, verification of numbers, inspection, exercise, or introduction into service.
      • 1598, William Shakespeare, King Henry IV, Part 1:

        Come, let vs take a muster speedily: / Doomesday is neere; dye all, dye merrily.

      • 1663, Samuel Pepys, Diary, 4 Jul 1663:

        And after long being there, I 'light, and walked to the place where the King, Duke &c., did stand to see the horse and foot march by and discharge their guns, to show a French Marquisse (for whom this muster was caused) the goodness of our firemen [...].

   3. A roundup of livestock for inspection, branding, drenching, shearing etc.
      • 2006, John Gilfoyle, Bloody Jackaroos!, Boolarong Press:

        McGuire took the two of them out to Kidman's Bore on the Sylvester River where about two dozen stockmen from different stations had gathered to tend the muster along the edge of the Simpson Desert.

2. Showing.
   1. Something shown for imitation; a pattern.
   2. An act of showing something; a display.
      • 1590, Sir Philip Sidney, Arcadia, Book III:

        Thus all things being condignely ordered, will an ill favoured impatiencie he waited, until the next morning he might make a muster of him selfe in the Iland [...].

      • 1647, Beaumont & Fletcher, The Queen of Corinth, Act 2:

        And when you find your women's favour fail, / 'Tis ten to one you'll know yourself, and seek me, / Upon a better muster of your manners.

   3. A collection of peafowl (an invented term rather than one used by zoologists).

Verb

1. To show, exhibit.
2. To be gathered together for parade, inspection, exercise, or the like (especially of a military force); to come together as parts of a force or body.
3. To collect, call or assemble together, such as troops or a group for inspection, orders, display etc.
4. To summon together; to get together, to gather.

   I mustered up all my remaining willpower.

5. To enroll (into service).