No, it's very similar to nemec, basically the same thing also borrowed from Slavic. The "c" ending is pronounced as "ts". The full phrase goes like: "Why don't you understand, are you German/Turk?" (as in not understanding the language). There's also a place, a citadel and river with that name, which your ancestors might have been familiar with:
https://en.wikipedia.org/wiki/Siege_of_Neam%C8%9B_Citadel
Barbar means what it means in Greek, because that's where it's borrowed from.