An Etymological Dictionary of the German Language/Annotated/heulen

by Friedrich Kluge

heulen, verb, ‘to howl, yell, scream,’ from Middle High German hiulen, hiuweln, ‘to howl, cry, Old High German hiuwilôn, hiwilôn, ‘to shout for joy.’ Also allied to Old High German hûwila, hiuwila, Middle High German hiuwel, feminine, ‘owl’ (as ‘the howling bird’), and hence more remotely to Old High German hûwo, masculine, ‘owl.’