An Etymological Dictionary of the German Language/Annotated/Brief
Brief, masculine, ‘letter, epistle,’ from Middle High German brief, Old High German brief, masculine; from Latin brĕvis (scil. libellus); the lengthened ê from ĕ in words borrowed from Latin becomes ea and then ie (compare Priester); Latin brevis and breve, ‘note, document,’ The High German word had originally a more general signification, ‘document,’ hence the Modern High German verbriefen. Middle High German and Old High German brief, ‘letter, document,’ and generally ‘a writing.’ When the Old Teutonic Runic characters were exchanged for the more convenient Roman letters (see schreiben as well as Buch), the Germans adopted some terms connected with writing; Old High German briaf appears in the 9th century (the Gothic word is bôka, ‘document’).