and new to me because all my German (and rest of language) namebooks give the "(free) man" meaning. The derivation from harj would have more sense because it is an usual element in Germanic names (and karl as onomastical element is a hapax, because it only appears in the family names of Charles).
I searched at BtN archives and I found one of your posts with Seibicke's explanation and its translation to English. Could you do the same with Kohlheim's explanation? Or is it just the same that Seibicke's one?