An Etymological Dictionary of the German Language/kennen
kennen, vb., ‘to know, be acquainted with,’ from the equiv. MidHG. kęnnen, OHG. chęnnen. The simple form was very little used in MidHG. and OHG., the usual words being the compounds OHG. irchęnnen, MidHG. erkęnnen, and OHG. bichęnnen, MidHG. bekęnnen, with the meanings of ModHG. kennen. The corresponding Goth. kannjan (uskannjan), as well as AS. cęnnan, gecęnnan, signifies ‘to make known.’ This double sense, which is combined in OIc. kenna, is explained by the fact that OTeut. kannjan is a factitive of the OTeut. pret.-pres. kann, inf. kunnan, ‘to know’; erkennen is a derivative ‘to inform oneself.’ Comp. further references under können.