Oh I still use it that way, though I never made the connection between the term and the German given name. I hope it’s not a slur, I had never thought of that. Hmm.
That’s common with English Cockney, where a rhyme is substituted for the original word or phrase, so that would make sense. But again I don’t think it’s common usage so the OP’s question is somewhat invalid. (At least as far as I can tell, I might be wrong.)