An Etymological Dictionary of the German Language/Bann
Bann, m., ‘ban, outlawry, decree,’ from MidHG. and OHG. ban (nn), m., ‘order under threat of punishment, prohibition; jurisdiction and its sphere.’ It corresponds to AS. bann, E. ban, and belongs to an obsolete str. vb. bannan, of which the primary meaning was ‘to order or forbid under threat of punishment.’ The root is supposed to be ba, pre-Teut. bha-; nn was perhaps a suffix (comp. rinnen), and properly belonged only to the pres. of the str. vb., but was afterwards joined to the verbal stem. To this pre-Teut. bha- belongs, in accordance with the permutation of consonants, Gr. φα in φά-σκω, φη-μί and Lat. fa in fari; the Teut. meaning must then have been very definitely specialised. From the Teut. word the Rom. cognate Fr. ban, ‘public proclamation’ (OFr. arban, ‘arrière ban’), is derived.