mid-14c., from Old French brievet "letter, note, piece of paper; papal indulgence" (13c.), diminutive of bref "letter, note" (see brief (n.)). Military sense of "a commission to a higher rank without advance in command" (for meritorious service, etc.) is from 1680s.
"confer brevet rank upon," 1803, from French breveter, from brevet (see brevet (n.)). Related: Breveted; breveting.