An Etymological Dictionary of the German Language/Gräuel
Gräuel, m., from the equiv. MidHG. griul, griuwel, m., ‘terror, horror, abomination’ (Du. gruwel); allied to ModHG. grauen, MidHG. grûwen, ‘to horrify, terrify,’ OHG. ingrûên, ‘to shudder.’ Akin also to ModHG. grausam, from MidHG. grûwesam, ‘exciting terror’; ModHG. gräulich, from MidHG. griuwelich. The root grû, ‘to frighten,’ is wanting in the rest of the OTeut. dialects. See Graus.