[Ger-Poland-Volhynia] The name Markowitz

[Fred & Ima Jean Markowitz]

Ermeland was the name of a region in old East Prussia running south of
the Baltic down through Heilsberg (now Lidzbark)--in the old Warmia
area.  My father, August Markowitz Jr, at age 6, with his parents and
siblings, emigrated from there in 1890 and settled in Kansas (USA).
They were woodworkers, that is, cabinet makers, wagon makers, and my
father in later life built houses.  In Ermeland, they lived in or near a
town or village named Freudenberg (now Radostowo, I think) south of
Heilsberg near BlankenSee (now Blanki Lake).  My grandfather's name was
Augustin, and my great-grandfather was Johannes (aka Johann).  The
Markowitz clan I am speaking about here were devout Catholics and most
remain so.  Their old language was German.  It seems that outside of
this Markowitz clan, almost all with that surname are Jewish.  They seem
to be concentrated on the eastern US coast but not exclusively.  All of
which leads me to these questions:  Were my predecessors generations ago
once members of the Jewish faith and converted to Catholicism (an event
that seems unlikely, but maybe not)?  Or were there branches of Germans
with the same surname but of different bloodlines and religious
beliefs?  Any insights?  'Tis a puzzlement.