from L. breve
), noun derivative of L. adj. brevis
(adj.)) which came to mean "letter, summary" (specifically a letter of the pope, less ample and solemn than a bull
), and came to mean "letter of authority," which yielded the modern, legal sense of "summary of the facts of a case" (1630s). The verb meaning "to give instructions or information to" (1866) was originally "to instruct by a brief" (1862); hence briefing
, first attested 1910 but popularized by WWII pre-flight conferences.