There was no such thing as a "mixed marriage" involving one Jewish and
one Gentile party in the 17thC. In fact, that was generally true in
Germany, Switzerland, etc. until at least the middle of the 19thC.
Conversion of one party would have to precede the marriage, and
conversion to Judaism was not an option in most places.
As to LEHMANN coming from Lac Leman (Genfer See/Lake Geneva), it's
unlikely, especially as nobody would have caught the reference. LEHMANN
is about as common a surname as the German-speaking world has, with
literally 10s of thousands of entries in the White Pages.
(dastelefonbuch.de) It means, literally, "liege man," i.e., a vassal.
Quite a few LEHMANNs in Germany were Jewish, but they made up at most 5%
of the total. And before around 1800, Jews generally didn't use surnames
at all, and those who did are not known to have used LEHMANN.
Nor is WILBERS known to have been used by any Jewish family in Germany.
(Source: Lars Menk, _A Dictionary of German-Jewish Surnames._) Again, if
the surname existed in the 17thC, and wasn't one of a small number of
surnames used by Jews in big cities, it's not a Jewish surname.
Roger Lustig, Princeton, NJ USA
Research coordinator, GerSIG