This is the 8079th most frequent Polish word.
nim
The Polish word "nim" means "him" or "it" (instrumental form of "on" or "ono").
The word 'nim' is used as an instrumental-case pronoun for 'he' in Polish, meaning 'with him' or 'about him', depending on the verb.
Rozmawiałem z nim o twoim problemie.
I talked with him about your problem.
Here, 'nim' serves as the locative-case pronoun for 'he', indicating location.
Czy widziałeś książkę za nim?
Have you seen the book behind him?
In this sentence, 'nim' is again in the instrumental case, attached to the verb requiring this case for the meaning 'with him' or 'agree with him'.