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 German consonants 

I do not recall specific examples of h and k swaps, but it seems possible to me. I know the cities of Kassel and Karlsruhe were often spelled Cassel and Carlsruhe in German in the 19th century (and Koeln was Coeln (Cologne)). There is also the whole issue of writing and being able to read it - Fraktur and Sütterlin are always tricky and h and k may look similar in them.   ><>°° "