If you read Deborah Tannen's book one of the things she talks about...when women talk to each other they nod. This is how women (normally) communicate. It is an indication of "I'm listening." If you look at a group of women talking they look like those dogs with the wiggly heads in the back of automobiles.

When men nod it is -- in "men speak" if you will, a sign of agreement.

The breakdown can occur when a woman is non-verbally saying "I am listening" and the man is non-verbally hearing "I agree with you."

And of course, when the man does not nod...women hear "not listening."

It is a very interesting area of study that crosses cultures as well.

And can be useful to understanding each other.

Perhaps this could be a visual that contributed to the term "hen party" all though I have never heard that term used in any "endearing" way!