This is the 8052nd most frequent Polish word.
niemnem
The word "niemnem" does not exist in the Polish language as a standalone term. It may be a typo or a misinterpretation.
here, 'Niemnem' refers to the Neman River, as part of the book's title.
Czytałem książkę pt. 'Nad Niemnem'.
I was reading the book titled 'Nad Niemnem'.
here, 'Niemnem' refers to the Neman River in a locative case form.
Pojechaliśmy na wycieczkę nad Niemnem.
We went on a trip by the Neman River.
here, 'Niemnem' continues to represent the Neman River, discussing its surrounding scenery.