c. 1300, bref, "of short duration;" early 14c., "small with respect to length, short;" from Latin brevis (adj.) "short, low, little, shallow," from PIE *mregh-wi-, from root *mregh-u- "short."
early 14c., bref, "a writing issued by authority," from Latin breve (genitive brevis), noun derivative of adjective brevis "short, little" (from PIE root *mregh-u- "short") which came to mean "letter, summary," specifically a letter of the pope (less ample and solemn than a bull), and thus came to mean "letter of authority," which yielded the modern, legal sense of "systematic summary of the facts of a case" (1630s). Sense of "a short or concise writing" is from 1560s. In German, Brief has become the general word for "an epistle or letter."