Muster

(intransitive) 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. from 15th c.

(transitive) To collect, call or assemble together, such as troops or a group for inspection, orders, display etc. from 15th c.

(transitive) To summon together; to get together, to gather. from 16th c.
I mustered up all my remaining willpower.

(transitive, US) To enroll (into service). from 19th c.