Don’t get tripped up by this when researching your German ancestors. Many times, German females would have “-in” added to their surnames. Thus, a woman with the last name of Schmidt might have sometimes been called “Schmidtin”. A woman with the last name of Mueller might have sometimes been called “Muellerin”. Their actual surname was not “Schmidtin” or “Muellerin”. The “-in” suffix is just designating that the person is a female. Their real surname would still be “Schmidt” or “Mueller,” in these instances.