An Etymological Dictionary of the German Language/Annotated/Narr
Narr, masculine, ‘fool,’ from Middle High German and Middle Low German narre, masculine, ‘simpleton, fool,’ Old High German narro, masculine ‘madman’; a word peculiar to German, the origin of which is totally obscure. The derivation from Middle Latin nârio, ‘sneerer, scoffer, subsannans,’ is not satisfactory, since the Latin word would be represented by a different form in German; moreover, there is no reason, as far as the meaning is concerned, to suppose that the word was borrowed (see Gaukler). Allied to Old High German snurring, Middle High German snürrine, ‘buffoon, fool’?.