debar (v.)

early 15c., "to shut out, exclude" (from a place), also "prevent, prohibit" (an action), from French débarrer, from Old French desbarer (12c., which, however, meant only "to unbar, unbolt," from des- "do the opposite of" (see dis-) + barrer "to bar," from barre "bar" (see bar (n.1)). The meaning turned around in French as the de- was felt in a different sense, perhaps as an intensifier. Related: Debarment; debarred.