I use to work in the courthouse, and they had a group of girls they called hens. It was because they gossip endlessly, always cackling, complaining or b#t#hing about something or someone, showed very little compassion to others unless it was a way to get closer to them to find out something to take back and gossip about. If they got upset/angry/peeved/whatever at somebody in their little click they would all pal up to one side and pluck the other person to death, almost as if they enjoyed watching them suffer in pain. Of course, they always had "some" target to torture.
The irony is they always denied their behavior, but others saw it, caught on to the game after awhile. They had their group, and they didn't extend beyond that. And, the group were the ones who had been there for years.
I was friendly to them, saw the head games, decided they were people I did not want to be close to or have any involvement with, because they seemed to lack the true meaning of being someone's friend.
After awhile, I became desensitized to the chatter. It started to sound like standing outside a hen house, just noise.
That was the only time I’ve heard the terminology until I came here to the board. Personally, I would find it insulting to be called a hen.