An Etymological Dictionary of the German Language/ahnen

by Friedrich Kluge

ahnen, vb., ‘to forebode, suspect,’ from MidHG. anen, ‘to foresee, forebode,’ foreign to the older period and to the rest of the Teut. dialects; it has been connected with the OAryan root an, ‘to breathe, respire,’ so that it may be a primit. cognate of ahnden, under the influence of which it also appears in ModHG. as ahnden. It is better, however, to regard it as a derivative of the prep. an; allied, lit. ‘to befall, seize, attack' (properly said of ghosts or visions).