An Etymological Dictionary of the German Language/heulen

by Friedrich Kluge

heulen, vb., ‘to howl, yell, scream,’ from MidHG. hiulen, hiuweln, ‘to howl, cry, OHG. hiuwilôn, hiwilôn, ‘to shout for joy.’ Also allied to OHG. hûwila, hiuwila, MidHG. hiuwel, f., ‘owl’ (as ‘the howling bird’), and hence more remotely to OHG. hûwo, m., ‘owl.’