An Etymological Dictionary of the German Language/Annotated/Kilt
Kilt, Kiltgang, in Alemannian ‘nocturnal meeting’; wanting in Middle High German. Compare Old High German chwiltiwërch, neuter, ‘evening work’; Old Icelandic kveld, neuter, ‘evening’ (in Iceland and Norway the usual word for evening, while aptann is used poetically and in stately prose). Anglo-Saxon cwyldhreþe, feminine, ‘bat,’ literally ‘evening swiftness,’ cwyldsęten, ‘evening.’ Hence qeldos, neuter, is the oldest word for ‘evening.’ The loss of the w after k is normal; compare feck, Rot, and Röder.