Hi Doug,
I don´t really see the word Bope as a family name in Germany or Luxembourg and don´t know if it would even fit in with this family.
I think a possibility is, that it was his "nickname". In Luxembourg, one word for Grandfather is "Bopi" and because the luxembourgian/german "i" and the english "e" are pronounced the same way, it could just be a misspelling. Perhaps the children/grandchildren didn´t really know anymore what the nickname they called him originally meant. But it is just a theory...
Kind regards,
Timo