An Etymological Dictionary of the German Language/Annotated/hohl
hohl, adjective, ‘hollow, concave,’ from the equivalent Middle High German and Old High German hol, adjective; compare Dutch hol, ‘hollow,’ Anglo-Saxon hol, Old Icelandic holr, adjective, ‘hollow’; English hole is an adjective used as a substantive, so too Anglo-Saxon, Old High German, and Middle High German hol, ‘cave.’ The relation of these cognates, which point to Gothic *hula-, ‘hollow,’ to the equivalent Anglo-Saxon holh, English hollow, has not been explained. The word is usually connected with the root hel (in hehlen), ‘to conceal by covering’; Gothic hulundi, feminine, literally the hiding place, ‘cave.’