An Etymological Dictionary of the German Language/Annotated/Haupt
Haupt, neuter, ‘head, chief, leader,’ from Middle High German houbet, houpt (also höubet), neuter, Old High German houbit, neuter; the Old Teutonic word for ‘head,’ supplanted in the 16th century by Kopf in all the German dialects (Kohl-, Krauthaupt, almost the only existing forms, are dialectal), while English and Scandinavian have retained the earlier form — Anglo-Saxon heáfod, English head (for *heafd), neuter, Old Icelandic haufuþ, later hǫfuþ, neuter, Swedish hufvud, Danish hoved, ‘head,’ Gothic haubiþ, neuter. Since all the Teutonic dialects point to an old diphthong au in the stem, of which û in Old High German hûba, ‘hood,’ is the graded form (compare Haube), the Aryan base must be koupot, and Latin căput, for which *cauput might have been expected, was probably transformed by the influence of a word corresponding to Anglo-Saxon hafola, ‘head,’ Sanscrit kapâla, ‘skull,’ an assumption also supported by Latin capillus, ‘hair (of the head).’ The Middle High German höubet (Luther Heupt), formed by mutation from Old High German houbit, is still preserved in zu Häupten, in which primitive phrase the plural curiously represents the singular.