An Etymological Dictionary of the German Language/Brief
Brief, m., ‘letter, epistle,’ from MidHG. brief, OHG. brief, m.; from Lat. brĕvis (scil. libellus); the lengthened ê from ĕ in words borrowed from Lat. becomes ea and then ie (comp. Priester); Lat. brevis and breve, ‘note, document,’ The HG. word had originally a more general signification, ‘document,’ hence the ModHG. verbriefen. MidHG. and OHG. brief, ‘letter, document,’ and generally ‘a writing.’ When the OTeut. Runic characters were exchanged for the more convenient Roman letters (see schreiben as well as Buch), the Germans adopted some terms connected with writing; OHG. briaf appears in the 9th cent. (the Goth. word is bôka, ‘document’).