Ernest Weekley, The Romance of Words (4th ed.)
“ There is a word ban, found in Old High German and Anglo-Saxon, and meaning, as far back as it can be traced, a proclamation containing a threat, hence a command or prohibition. We have it in banish, to put under the ban. The proclamation idea survives in the banns of marriage and in Fr. arrière-ban, "a proclamation, [73] whereby those that hold authority of the king in mesne tenure, are summoned to assemble, and serve him in his warres" (Cotgrave) . This is folk-etymology for Old Fr. ”
