An Etymological Dictionary of the German Language/Annotated/Dünkel
Dünkel, masculine, ‘fancy, imagination, arrogance, prejudice,’ simply Modern High German. Related to the verb dünken, from Middle High German dunken (preterite dûhte), ‘to seem, appear to,’ Old High German dunchan (chiefly impersonal with dative), ‘to seem’ (preterite dûhta); Gothic þugkjan, þûhta, mostly impersonal with dative ‘to seem’; Anglo-Saxon þyncan, English to think, which, however, really represents the meanings of Anglo-Saxon þencan, Old High German, Middle High German and Modern High German denken. Dünken appears to have been originally a strong verb, of which denken was perhaps the factitive form. The Teutonic þunk, þank, is based upon an old Aryan root tng, teng, and this, again, appears in Old Latin tongêre, ‘to know’ (compare Prænestine tongitio, ‘notion’). Compare denken, Dank.