This is not an easy word.
At a first glance we could think, because of its ending ־נו, of this being a first person plural form: we...
But then... the verb would be נָבַח, would it not? And what does נָבַח mean? It means to bark.
Now, concept "bark" would rather be something odd in this context. No dog, no barking animal has been mentioned before.
This is a sign that this is not the good way to get the true meaning of this word.
Maybe our word is a PS-t word type? If so, the root letters would be בחנ.
Verb בָּחַן means examine, inspect, inquire into.
Let us suppose we are not able to see what really this word is. Oham gives nine possibilities. Surely one of these would offer the solution we need.
So, they (males, females or both) were examined.